Infiniti G-Series (Q40/Q60)

The Infiniti G-series is a line of compact executive/entry-level luxury carproduced by the Infiniti division of Nissan for the 1990–1996 and 1998–present model years. The first two generations of the Infiniti G (P10 and P11) were sedans based on the Nissan Primera. Beginning with its third generation (V35), the Infiniti G have been rebadged versions of the Nissan Skyline line of sedans and coupes that were exported to the United States and Canada. The current incarnation is the fourth generation (V36) which introduced the hardtop coupe convertible. The Nissan FM platform, on top of which the third and fourth generations (V35 and V36) of the Infiniti G have been built, also underpins the Nissan 370Z and has shared components with the Infiniti M, Infiniti EX, and Infiniti FX.

In May 2013, Infiniti announced a new naming convention beginning with the 2014 model year; all passenger cars are designated by the letter "Q," while sport-utility model names will begin with "QX." The Infiniti G was to have been replaced by the Infiniti Q50, but the G37 was revived as the Q40 beginning with the 2015 model year.

First generation (P10, 1990–1996)
The Infiniti G20 was Infiniti's entry-level luxury car in the United States during most of the 1990s and into the 2000s. Similar to the Japanese/European market Nissan Primera sedan, itself a luxury package of the Nissan Pulsar, the G20 offered higher levels of standard equipment. It was launched in September 1990 as Infiniti's first small car as an entry-level alternative to the Q45; later advertisements emphasized its European heritage with the tag line "Born in Japan. Educated in Europe. Now Available in America." Two generations of the G20 exist in the United States, the HP10 (P10), built from 1990 to 1996, and the HP11 (P11), built from 1998 to 2002. All G20s werefront-wheel drive and were built in Oppama, Japan. The exterior and interior designs were styled by Mamoru Aoki in 1988.

The G20 was first unveiled to Infiniti dealers at the 1989 New York International Auto Show (appearing to the public at the 1990 show), with the first series production example being assembled on July 10, 1990. The final 1996 G20 was rolled off the assembly line on July 19, 1996. The P10 featured the first application of Nissan's multi-link front suspension in a front-wheel-drive car, with an independent MacPherson strut setup in the rear. It came standard with a 5-speed manual transmission. The only options to begin with were an automatic transmission, leather interior, and a power glassmoonroof; a Touring package (labeled G20t) was introduced in 1994 and featured a black leather interior with sport front bucket seats and fold-down rear seats, as well as a limited-slip differential in the transmission and a spoileron the rear decklid.

Engine design
The G20 was powered by the SR20DE Inline 4-cylinder. It was a transverselymounted dual overhead cam naturally aspirated reciprocating internal combustion engine. Displacement was 2.0 litre (1998 cc) with a square (Bore × Stroke: 86.0 × 86.0 mm). This engine was also shared with the US-spec Nissan Sentra/Nissan 200SX SE-R, Nissan NX2000, and a host of non-US Nissan vehicles. The particular version used in the G20 produced 140 hp (100 kW) crank in the US at first, and 145 hp (108 kW) in '00+ editions (116 to 126 whp; stock range) and 132 lb·ft (179 N·m) or 136 lb·ft (184 N·m) torque (111 to 120 wft·lbf; stock range). These engines were also fairly high-revving with aredline of 7500 rpm for 1991 through 1996 models, 6950 rpm for the 1999 model, and 6750 rpm for 2000-2002 models. Due to the SR20DE engine's flexibility, reliability, fuel economy and high power-handling capabilities, as well as a low buy-in cost, pre-owned NX2000, SE-R powered Sentras/200SXs and G20s have become popular and prominent in the "tuner" or "import scene" subculture.

There were three major variants of the SR20DE used in the G20. The first, used from July 1990 to December 1993, was the highport, in which the injectors and fuel rail were located above the intake plenum. In January 1994, due to tightening emissions restrictions, Nissan switched to a lowport design, in which the injectors and fuel rail switched places with the intake plenum. This design also featured a milder intake camshaft. (Switching it out for the highport intake cam is a popular upgrade to gain more power.) This design was used from 1994 to 1996 and again in 1998. In 1999 Nissan replaced the valvetrainwith a roller-rocker arm lifter design in place of the hydraulic rocker arm previously used, but kept the lowport intake design; many performance parts are not interchangeable between roller-rocker and highport/lowport engines, most notably camshafts.

Transmission
The G20 featured either a 5-speed manual transmission or an optional 4-speed automatic. Stock manual transmissions are typically usable up to approximately 250 whp, while stock automatic transmissions can only handle about 155 whp. Most front wheel drive transmissions from other SR-powered cars can be used with few modifications. The stock transmission as well as other SR20 transmissions are often upgraded with various modifications in order to handle more power. Common manual transmissionmodifications include cryo treating, shot peening, transmission case welding, aftermarket limited slip differential, aftermarket axles, and upgraded clutches. Common automatic transmission modifications include built valve bodies, aftermarket torque converters, automatic transmission fluid (ATF) coolers, additional ATF filters, and aftermarket TCUs. Higher rated transmission swaps from front-wheel drive VQ or QR25DE powered cars such as the 2002–2006 Nissan Sentra SE-R Spec-V have also been performed.

Equipment
The G20 was a badge-engineered version of the Nissan Primera, but because Infiniti was pitched as a premium brand, it featured a high level of equipment compared to its European and Japanese relatives. The only engine available was the 2.0 litre SR20DE Inline 4-cylinder; in Europe this was the top-of-the-line engine for the Primera lineup. 5-speed manual and 4-speed automatic transmissions were both available, with the 5-speed being praised as "one of the best in the business." Power windows, power locks, power mirrors, air conditioning, four-wheel disc brakes with ABS, alloy wheels, a Bose stereo, atheft-deterrent system, cruise control, floor mats, and a leather-wrapped steering wheel and gearshift knob were all standard. Heated mirrors, leather seats and a power moonroof were common options, and were later offered in a package that included power seats and keyless entry. Later models also featured dual front airbags. The standard trim was called Luxury. Two major trim package upgrades were offered: Touring, badged G20t, available from model years 1994 to 1996 and 1999 to 2001, and Sport (with no badge modification) which was offered during model year 2002. These packages featured a limited-slip differential in the transmission, sportier, more highly bolstered front bucket seats and fold-down rear seats, all-black leather interior, fog lamps, and a spoiler on the rear decklid. The details of these trims varied from year to year.

P10 model refresh changes
Introduced at the 1993 New York Auto Show, the main changes for the P10 came as a midyear refresh in April 1993 (model year 1993.5), when dualairbags replaced motorized seatbelts, leather interiors came standard with power front seats, matte-black side moldings were replaced by body-colored ones, the refrigerant was converted from R12 to R134a, the audio system was upgraded to six speakers with a CD player instead of the previously-standard cassette deck, and other new options such as remote keyless entry were added. In February 1994, the 1994 model year was given a new larger chrome-plated grille and door handles, a lowport engine (replacing the original highportSR20DE, in which the intake plenum is below the fuel injectors and fuel rail), a change in the vehicle's self-diagnostic system to OBD-II, and larger 195/65R14 tires. The Touring models, introduced in February 1994, featured a limited-slip differential in the transmission; 195/65R14 Yokohama tires, sportier, more highly bolstered black leather front bucket seats and fold-down rear seats; fog lights; and a spoiler on the rear decklid. The G20 was temporarily discontinued after the 1996 model year, leaving theI30 as Infiniti's lowest-priced car for the 1997 & 1998 model years.

Second generation (P11, 1998–2002)
The second-generation G20 underwent several changes, including adopting themulti-link beam rear suspension very similar to the 1995–1999 Nissan Maximawith a continued use of the independent multi-link strut front suspension of the P10 (similar to the 300ZX and Skyline GT-R). Despite enthusiasts' aversion to the beam, several publications praised the of the updated G20, as a technically good method of avoiding lateral suspension movement (which would compromise handling) while still offering a compliant ride. The P11 has a lateral grip figure of between 0.80 and 0.94g plus a 61/39 weight distribution (61% front/39% rear). It grew in size, with a 2.7-inch (69 mm) length increase and 0.4-inch (10 mm) height increase over the P10, resulting in 1.4 inches (36 mm) more legroom for rear-seat passengers. The new model's increased size and luxury options, however, added to the car's weight (which rose to 3000 pounds); the stock 140-145 crank horsepower engine provided lower performance (the MY1999 automatic, for example, had a 10.9-second 0-60 mph time and did the quarter-mile in 18.4 seconds at 77 mph (124 km/h).

The first example of the second-generation G20 rolled off the Oppama assembly line on May 18, 1998, going on sale in July 1998 as a 1999 model. The final second-generation 2002 G20 was assembled on January 11, 2002 and the G20 slowly phased out during the first quarter of 2002, in being replaced by the 2003 model year rear-wheel drive G35 sports sedan. All models featured a higher level of standard equipment than the P10, including automatic climate control on all but cloth-seat Luxury models, 15" 16-spokealloy wheels, a higher-quality double-DIN Bose radio/CD/cassette player standard, keyless entry, standard power moonroof, and later, side-impact airbags. The Touring models continued to feature a limited-slip differential, but also had unique 12-spoke alloy wheels, and the upgraded sports seats were now available in beige leather and "sport cloth" (the latter as a factory-order option) in addition to the previously-offered black leather.

P11 model refresh changes
In late 1999, several noteworthy changes for the P11 came as a refresh in the 2000 model year, when the 145 crank horsepower roller rocker variant of the SR20DE engine was implemented, newer automatic and manual transmission variations were introduced, anti-theft immobilizer circuitry was added, anti-glare side mirrors became standard, and a remote trunk release was added to the keyless entry fob. In 2001, the G20t was dropped and a Sport model was introduced. In addition to the prior G20t's limited slip differential and decklid spoiler, this model featured two-tone leather/suede sport seats, 16" wheels, and a variety of minor cosmetic modifications. The 2002 base G20 received the 12-spoke Touring alloy wheels as standard.

End of production
The G20 was discontinued in favor of 2003's rear wheel drive Infiniti G35, abadge engineered export version of the JDM V35 Nissan Skyline which was introduced in Japan in 2001. The G35 received significant praise from the automotive press and became a sales success for Infiniti despite being priced approximately US$7,000 above the G20's average MSRP of $23,000. The G35, significantly larger and more powerful than the G20, was aimed more at the entry level premium-sports sedan market instead of the G20's premium-sport compact market. The Nissan Primera was continued outside the United States as the slightly restyled HP11-144 and the significantly restyled HP12 markets with a final end to all production in 2006 as a 2007 model.

Third generation (V35, 2002–2007)
The third generation G (V35) was unveiled in June 2001 and released to North America for the 2003 model year, as the G35 in early 2002. It had little in common with the Infiniti G20, and continued in the same tradition as theoriginal Infiniti M and the J30, which were also RWD models utilizing the same drivetrain as contemporary Nissan Zs. According to Carlos Ghosn, CEO ofNissan Motors, the letter G was chosen "for marketing purposes and its similarity in sound to the letter J", apparently in deference to the Infiniti J30. Hiroshi Hasegawa designed both the sedan (finalized in 1999) and coupe (finalized in late 2000), with the former being previewed as the Nissan XVL Concept sports sedan in October 1999 at the Tokyo Motor Show and Infiniti XVL Concept in January 2000 at the NAIAS.

G35
The G35 is based on the Nissan FM platform shared with the Nissan 350Zsports car and Infiniti FX crossover SUV. The FM platform stands for "front midship" design where the engine is moved back towards the rear of the engine bay which in turn improves the weight distribution. The G35 was Motor Trend'sCar of the Year for 2003 and has been well received by both the media and customers as a viable alternative to other luxury cars. The G35 was also nominated for the North American Car of the Year award that year and was on the Car and Driver Ten Best list for 2003 and 2004.

Sporting the ubiquitous VQ35DE engine, the Infiniti G35 uses a front-midship engine, rear-wheel drive layout (all-wheel drive is available for the G35x sedan) to achieve a 52% front/48% rear weight distribution. Both body styles are available with either a 5-speed automatic or 6-speed manual transmission, although the automatic is the only transmission available for the AWD sedan.

A 6-speed manual transmission became available in 2003 as a 2004 model on the sedan (the coupe always had the option). For the 2003-04 model years, theV6 produced 194 kW (264 PS; 260 hp) and 353 N·m (260 lb·ft) of torque in the sedan, 209 kW (284 PS; 280 hp) and 366 N·m (270 lb·ft) in the coupe. In the 2005 and 2006 model years (sedan, 2005-2007 for the coupe), those with automatic transmissions (both sedan and coupe) produced 209 kW (284 PS; 280 hp) and 366 N·m (270 lb·ft) of torque, while those with manual transmissions produced 222 kW (302 PS; 298 hp) and 350 N·m (258 lb·ft) of torque (again, both in sedan and coupe form). There is speculation that the output did not actually change, and that Infiniti was simply taking advantage of the outdated SAE standard of rating horsepower. It should, however, be noted that manual transmission cars received a slightly different engine versus those fitted with automatics; manual cars had engines fitted with variable valve timing on both intake and exhaust camshafts, wheres automatic cars only have VVT on the intake side. The G35 is assembled in Tochigi, Tochigi, Japan, and the first G35 was built on March 12, 2002 as a 2003 model.

The AWD model of the G35 sedan is called the G35x. Although the automatic transmission for the G35x is manufactured by Aisin-Warner, the AWD technology uses Nissan's proprietary ATTESA E-TS AWD system. The system will make the car 100% rear wheel drive when driving at a steady speed. When the driver uses the throttle to accelerate from a stop or constant speed, the AWD system can send up to 50% of torque to the front wheels. When the car's speed becomes steady again, the drivetrain will return torque to the rear wheels. The AWD system will also transfer torque to the front wheels if the system detects loss of traction. This technology was first used in the 1989Nissan Skyline GT-R, and has since been used in subsequent Skylines, and other vehicles in Japan and overseas, including the Nissan Bluebird, andNissan Stagea. There are few differences between the 2003 & 2004 G35 coupes. Both '03 & '04 six-speed manual models had the option of Brembo brakes and the Performance Tire and Wheel Package. On the 2005 coupes, three new colors, 'Athens Blue', 'Lakeshore Slate', and 'Serengeti Sand', replaced 'Twilight Blue', 'Caribbean Blue', and 'Desert Platinum' respectively; also, the Willow Cloth interior option was removed, and Stone leather became available.

2005 and 2006 refreshes
The G35 sedan was refreshed inside and out for the 2005 model year and the coupe for the 2005 and 2006 model years. The interior was given sportier gauges with better backlighting and higher quality trim and knobs. Genuine aluminum trim replaces "tinted" interior trim, and the dash and center console layout were revised. Rosewood trim becomes available as a package on the 2005 models. MP3/WMA playback was added to the now standard 6 disc in-dash CD player, and the cassette player was removed. Brembo brakes were removed for the 2005 and 2006 models, and the brakes were redesigned with larger discs and a different caliper design. This was partly in response to a number of complaints about the previous years' brakes, which included a class action lawsuit filed in California related to premature wear on 2003–2004 models. A sport-tuned suspension package was standard on all six-speed manual equipped models, which included a viscous limited slip differential and the higher output VQ35DE "Rev-UP" engine. The 2006 models received minor updates. On the exterior there were new headlights, taillights, spoiler, sport side sills, and front bumper. Bluetooth capability was added to the interior for hands-free phone use. Rear active steering was an option for the '06 coupe.

Fourth generation (V36, 2006-2015)
The five-year development program for the V36 began in 2002, with conclusion in 2006 for the sedan and 2007 for the coupe. Design work started in 2003 and continued into 2004, when Hideo Komuro's design was chosen for the sedan. The coupe design process was later completed in the first half of 2005, with a conceptual variant being readied for public introduction. The redesigned InfinitiG sedan and coupe were introduced for the 2007 and 2008 model years, respectively. The fourth generation G sedan was launched in November 2006 as a 2007 model with a heavily revised 3.5 L VQ35HR engine and a 5-speed automatic as the standard transmission, a 6-speed manual was also available. The redesigned second generation G coupe launched in August 2007 as a 2008 model with a larger 3.7 L VQ37VHR, the first Infiniti engine to feature VVEL. It too came with either a 5-speed automatic or 6-speed manual. All manual G models include a sport package. The 2009 G37 convertible was launched in June 2009. The 2009 model G sedan followed suit using the same VQ37VHR engine. Also for 2009 the 5-speed automatic was replaced with an all-new 7-speed and both the sedan and coupe gained a self-healing paint finish from theInfiniti EX. The V36 platform continued for 2010 with numerous interior changes and upgrades as well as a mid-product cycle exterior update for the sedan. In late 2010 the Infiniti G25 went on sale as a 2011 model, featuring a smaller 2.5L version of the VQVHR engine to allow the G to better compete with the Lexus IS250 and BMW 328i.

2007–2008 G35 Sedan
The G35 sedan underwent a major revision for the 2007 model year. This 2nd generation front-mid (FM) platform underpinning the new G is shared in part with the Infiniti M and has several structural reinforcements around the engine and rear floor area, along with three times more laser welding and 16 percent more spot welds than the old version; overall body stiffness was improved by 40 percent. Single-pivot lower control arms in front replace the 1st gen model's twin lower links. The G35x sedan uses an ATTESA E-TS all-wheel drive system.

Along with these chassis refinements, Sport package equipped models came with firmer rear shocks, bigger front brake calipers, and larger 13-inch (330 mm) rotors all around (up from 12.6/12.1-inch front/rear). Sport package equipped cars also get a viscous limited slip differential. An all-new Active Steering package can be ordered for sport package equipped models. It features a planetary gearset on the steering shaft (similar to BMW), that varies the steering ratio between 12.0:1 and 18.5:1. A rear-wheel steering system that induces up to one degree of rear steer is also included in this package. The Active Steering package includes even stiffer shocks than the sport package at all four corners and the ride has been repeatedly reported as being too stiff for most customers except the most "enthusiastic" drivers. Base and Journey model 17-inch (430 mm) tires bump up from 215s to 225s, while the 18-inch (460 mm) upgrade (included in sport or wheel package) with 225/50-ZR18 front and 245/45-ZR18 rear is now a size smaller in front and larger in back than the 1st gen model's all-around 235/45R18s.

The updated VQ35HR is more powerful (306 hp (228 kW) at 6,800 rpm and 268 lb·ft (363 N·m) at 4,800 rpm), more fuel efficient, and more responsive than the previous VQ35DE. The "HR" stands for "High Revolution" or "High Response". A dual-path intake (two air cleaners, throttle bodies, etc.) lowers intake tract restriction by 18 percent and new equal-length exhaust manifolds lead into mufflers that are 25 percent freer flowing. The intake is said to benefit from a ram-air effect adding three horsepower at 60 mph. Electrically actuatedvariable valve timing is new on the exhaust cams which broadens the torque curve. The new engine block maintains the same bore and stroke, but the connecting rods were lengthened and the block deck was raised by 8.4 mm to reduce piston side-loads. 80% of the internal components have been strengthened or redesigned to handle the increased 7,500 rpm red line, along with the use of larger crank bearings with main bearing caps reinforced by a rigid ladder-type main cap girdle. With an increase in compression ratio from 10.3:1 to 10.6:1 these changes add 26 more horsepower. Torque is down 2 pound force-feet (2.7 N·m) from the old DE engine (268 vs. 270). The engine now sits 15 mm lower in the chassis for a lower center of gravity.

Although the horsepower rating increases only 8 hp compared to the latest version of the previous "DE" engine, the real horsepower difference was much greater due to Nissan adopting the 2006 SAE hp measurement guidelines for horsepower ratings in 2007. According to Consumer Reports an Infiniti G35 Journey sedan with a 5-speed Automatic transmission can reach 0–60 mph (0–97 km/h) in 5.4 seconds, and the 1/4-mile (~400 m) 13.8 seconds. According to the also newly revised EPA guidelines, fuel economy is estimated at 17 mpg-US (14 L/100 km; 20 mpg-imp) in the city and 24 mpg-US(9.8 L/100 km; 29 mpg-imp) on the highway. Fuel economy is virtually identical between generations, with the second generation earning a 1-mile-per-US-gallon (0.43 km/L; 1.2 mpg-imp) edge in highway driving (both measured using EPA 2008 guidelines).

Second generation G35 performance: According to Motor Trend and Automobile Magazine,a previous model 2005 G35 6MT sedan reached 0-60 mph in 5.7 seconds and the 1/4-mile in 14.1 seconds. This gives the new 2nd gen G35 V36 sedan a solid 0.4 and 0.3 second performance advantage respectively. Five Speed automatics are on par with manual transmission cars from a performance perspective. In a 2008 Road & Track comparison testwith the new 2008 Cadillac CTS a 5-speed automatic transmission equipped G35 sedan achieved a 0-60 time of 5.3 seconds, a 0-100 time of 13.1 seconds and a 1/4-mile time of 13.8 seconds at 102.9 mph (165.6 km/h). Generally a V36 G35 reaches 60 mph in the low 5 second range; 100 mph in around 13 seconds and runs the quarter-mile in about 13.8 seconds. The 200 lbs. heavier all wheel drive versions are only approx. 0.3 seconds behind in each of these measurements.

Models (including the since 2009 G37): In addition, a special edition of the G37 was entered into the SEMA Gran Turismo Awards in 2008.
 * G35/G37 - 3.5/3.7 L V6, 306 hp (228 kW) / 328 hp (245 kW),
 * G35/G37 Journey - 3.5/3.7 L V6, 306 hp (228 kW) / 328 hp (245 kW), weight 3,628 lb (1,646 kg)
 * G35x/G37x AWD - 3.5/3.7 L V6, 306 hp (228 kW) / 328 hp (245 kW) 4WD, weight 3,882 lb (1,761 kg)
 * G35/G37 Sport 6MT - 3.5/3.7 L V6, 306 hp (228 kW) / 328 hp (245 kW), weight 3,709 lb (1,682 kg)
 * G37 Convertible - 3.7 L V6, 325 hp (242 kW), weight 4,083 lb (1,852 kg)
 * G37 Convertible Sport 6MT - 3.7 L V6, 325 hp (242 kW), weight 4,149 lb (1,882 kg)

Infiniti Coupe Concept (2006)
Developed from mid-2005 to November 2005, it was a concept vehicle that previewed the design of the V36-based G coupe. It included a full-length glass panel roof, modulated front fenders and hood, deep front spoiler and large projector headlights, polished bare metal-look paint, compact camera outside rearview mirrors, hidden door handles and large 20-inch, 9-spoke painted aluminum-alloy wheels.

The vehicle was unveiled in 2006 North American International Auto Show.

2008 G37 Coupe
In 2007, the redesigned G coupe was unveiled at the 2007 New York International Auto Show and was available for sale as a 2008 model. Unlike the 2007 and 2008 G sedan it was given the new 3.7 L 330 hp (250 kW)V6 VQ37VHR engine but for this one model year still paired with the 5-speed automatic transmission and was named the "G37." In Japan, the G37 joined the updated G Sedan under the Nissan Skyline (V36) nameplate. This also marks the first use of Nissan's VVEL (Variable Valve Event and Lift) system on a production vehicle in the US market.

2009-2013 G37 Sedan and Coupe
For the 2009 model the G35 sedan was replaced by the G37 sedan. The G37 sedan was first unveiled at the Geneva Motor Show for the European market. Exterior, interior and options remain identical to the 2008 G35 model range but the sedan now also sports the 3.7-liter VQ37VHR "VVEL" V6, rated 328 hp (245 kW) at 7,000 rpm and 269 lb·ft (365 N·m) at 5,200 rpm that was previously introduced in the G37 Coupe. Although the engine gains only 0.2 kg·m (2 N·m; 1 lb·ft) torque over the VQ35HR and this torque value arrives at a later 5,200 rpm vs. 4,800 in the VQ35HR, the torque curve itself is improved and flattened across the rpm range via Nissan's new VVEL (Variable Valve Event and Lift) variable valve timing resulting in better throttle response and low rpm torque. The G37s VQ37VHR engine has been touted by car magazines and reviewers as an improvement over the VQ35HR engine mostly adding much more refinement and smoother engine operation, especially at high rpm where the VQ35HR engine was frequently criticized for NVH and sounding strained, harsh and loud. The often criticized too aggressive clutch engagement, notchiness of the 6-speed manual in the G35 and engine vibrations transferred through the shifter and pedals in the G35 6MT cars was also addressed in the new G37 models.

All 2009 models came standard with Infiniti's new seven-speed automatic transmission that was also introduced on the 2009 FX35 and FX50, updated from the previous five-speed transmission. The G37 Sedan or Coupe could be equipped with a six-speed manual transmission by specifying the Sport 6MT model. The Base, Journey and X models could not be ordered with manual transmissions, however the Sport Package included all sport options of the 6MT model (excluding the manual transmission and the hand lever parking brake), and was available for the Journey and X models.

The 2009 sport package (standard on Sport 6MT cars, optional on Journey and X models) now also included larger sport brakes with 4-piston front/2-piston rear calipers with 14-inch (360 mm) ventilated front rotors and 13.8-inch (350 mm) ventilated rear rotors, a new sport wheel design 18-inch (460 mm) for the Sedan and 19-inch (480 mm) on the Coupe, and Viscous Limited-Slip Differential (VLSD). The Sport Package on G37 x AWD Sedans does not include the larger opposed piston brakes, nor does it include the more aggressive steering rack, VLSD, or sport tuned suspension (the same package for AWD Coupes includes everything from the RWD version, save the more aggressive steering rack). Brakes on non-Sport models are front 13-inch (330 mm) ventilated discs and rear 13-inch (330 mm) ventilated discs with sliding calipers. The G37 is available as G37, G37 Journey, G37S 6MT and G37x AWD models. Major option packages remain to be the Premium Package, Sport Package, Nav Package, Tech Package. All 2009 models come standard with self healing "Scratch Shield" paint which employs a soft polymer top coat that can self heal small scratches and swirl marks.

Even though the final drive ratio for vehicles equipped with the 7-speed automatic has been (numerically) reduced from 3.69 to 3.36, the new 7-speed automatic has much lower first through fourth gear overall ratios than the old 5-speed automatic and the 6-speed manual in the 6MT cars (which retain the old 3.69 final drive ratio). Giving it closer gear ratios in all gears, to match engine rpm better with power demand, brings better acceleration while overdrive ratios in 6th and 7th gears reduces highway cruising rpm and improves fuel mileage. The new 7-speed automatic retains the Drive Sport (DS) shift mode and Downshift Rev Matching (DRM) feature of the previous 5-speed automatic. Paddle shifters are standard on G37S models equipped with the 7-speed automatic. The new engine/transmission combo did add some weight the car (3,590 lb. for the G37 vs. 3,508 for the G35 in identical trim).

G37x Coupe uses an ATTESA E-TS all-wheel drive system.

G37 coupe and sedan were set on sale in September 2008 as 2009 models.

G37x Coupe and G37 sedan were unveiled in 58th annual Pebble Beach Concours d'Elegance. Pictures of G37 convertible was first shown in Monterey, while the vehicle itself would be unveiled in 2008 Los Angeles Auto Show in November.

The 2009 Infiniti G37 Anniversary Art Project Vehicle - This is a version of G37 Sport Coupe inspired by Cirque du Soleil to commemorate Infiniti's 20th anniversary. The vehicle was designed by Montreal artist Heidi Taillefer. The vehicle was set on tour at various Cirque du Soleil shows and other events, with eventual vehicle sale at charity auction.

2009-2013 G37 Convertible
G37 Convertible was introduced in June 2009 Media Release as a 2009 model on the V36 FM platform and is only from a design perspective based on the G Coupe.

The G Convertible came equipped with a standard 325 horsepower (242 kW) 3.7-liter V6, backed by a choice of a 7-speed automatic transmission with available magnesium paddle shifters or a responsive close-ratio 6-speed manual transmission. The G Convertible has a curb weight of 4,149 lb (1,882 kg).

Facelift
The facelift model 2011 G37 Convertible (US)

2010-2011 Infiniti G37 sedan (Germany)

From November 2009, a facelift for the 2010 model year G Sedan commenced production and went on sale in January 2010. Changes include a revised fascia with fog lamps moved from the head light cluster to the more traditional separate housings, a new grill for the sedan, a new optional navigation system for both the coupe and sedan (revised from the optional system available with the 2008 and 2009 G37s), and other minor changes. Several items that were options on the 2008 and 2009 models became standard on the 2010 G37s.

In a March 2010 comparison test by Car and Driver, the Infiniti G37 Convertible came in third place out of four cars in a convertible comparison behind theBMW 328i and Audi A5.

In July 2010, the Coupe and Convertible received a refresh for the 2011 model year.

2011-2012 Infiniti G25
Infiniti debuted the G25 sedan at the 2010 Paris Auto Show. The G25 was powered by a 2.5 L V6 VQ25HR producing 218 hp (163 kW) and 187 lb·ft (254 N·m) of torque. In a Motor Trend 2012 comparison the Infiniti accelerated from 0-60 in 7.5 seconds, almost 2 seconds slower than its bigger brother, the G37. The G25's JDM relative, the Nissan Skyline 250 GT Sedan which features the same engine, had been on sale for several years already.

Priced lower than the G37, the G25 was aimed to compete with entry-level luxury rivals such as the Lexus IS250, Audi A4 and BMW 328i. Compared to the G37, other than a smaller engine and fewer options (no six-speed manual transmission available, no Navigation, no Premium or Technology packages in the U.S. market), the G25 was otherwise identical and features a choice of rear-wheel drive or ATTESA all-wheel drive.

In 2012, the G25 was discontinued in the United States.

Infiniti Performance Line (IPL)
In July 2010 Infiniti released its new performance division, Infiniti Performance Line (IPL). The debut IPL offering is the G37 Coupe for 2011 model year, and later the G37 Convertible. The IPL models featured a retuned engine producing 348 hp (260 kW), more aggressive body kits, new alloy wheels, retuned suspension for better handling, a few other minor tweaks. Inside, the IPL G37 has red Monaco leather seats. The IPL G37 Coupe and Convertible are only available in 2 colours; Graphite Shadow gray metallic and Malbec Black. Like the regular models, the IPL G37 was also renamed IPL Q60 beginning 2014 model year.

Infiniti Q40
The Infiniti G sedan was renamed to Q40 for the production period between June 2014 and June 2015. This was due to the creation of and gradual implementation of the new nomenclature from September 2012 through 2014. The G/Q40 sedan went largely unchanged for its final year and final production run in 2015.

Infiniti Q60
The Infiniti Q60 is the coupe and convertible replacement for the Infiniti G37 coupe and convertible, and was released in July 2013. Similar to the Q40, the only difference between the older models is the change in nomenclature.

Infiniti Q50
The Infiniti Q50 is the replacement for the Q40.

Main article: Infiniti Q50

The 2014 model year replacement of the fourth generation G sedan code-named "V37" made its debut at the 2013 North American International Auto Show (NAIAS) and was named Q50.

Safety
The current generation of the G features standard dual front airbags, front and rear side curtain airbags, and front side torso airbags. It was rated "Good" for each the "Front Offset" and the "Side Impact" crash tests while rated "Acceptable" for "Roof Strength" by the Insurance Institute for Highway Safety(IIHS)Infiniti G IIHS safety ratings. However, an IIHS Status Report, released in 2007, ranked the 2003-4 Infiniti G35 as the safest car in the Luxury Mid-size category and the second safest vehicle overall, based on its observed fatal-accidents rate.

Awards and recognition
The G has earned many automotive awards over its lifespan:
 * Car and Driver: 1991 (April & September) High marks for suspension and value.
 * IntelliChoice: 1993 “Best Overall Import Car Value Over $13,000” and “Best Value in Compact Class Over $16,000.”
 * J.D. Power and Associates: 1996 Top Score in Customer Satisfaction Index.
 * J.D. Power and Associates: 1997 Second Highest Scorer in Customer Satisfaction Index.
 * IntelliChoice: 1999 G20 and G20t “A Best Overall Value - Compact Sedan Over $15,000.”
 * Consumer Reports First Place: Top 10 Cars (upscale sedan category) for 2007 and 2008
 * CAR Magazine: Rated One of the Top 10 Best Handling Cars in the World (P11)
 * Car and Driver "10 Best Cars" list: 2003, 2004, 2007, and 2009.
 * Nominated for the 2003 North American Car of the Year.
 * Motor Trend 2003 Car of the Year