The "M" nameplate has been used on various mid-luxury cars from the Infiniti luxury division of Nissan.
The first iteration was the M30 Coupe/Convertible, which were rebadged JDM Nissan Leopard.
First Generation: 1989-1992
The Infiniti M30 (chassis code F31) was a 2-door GT coupe introduced with the Q45 as the start of the Infiniti line in 1989, as a stopgap until other models could be produced. The M30 was basically a Japanese Nissan Leopard built with left-hand drive and rebadged as an Infiniti, and had added luxury features. The other main changes were in the engine, transmission and suspension. The M30 was only sold in the United States.
The M30 had no factory options, but dealers offered the addition of a cellular phone and a CD player/changer. The sole engine was Nissan's VG30E, a 3.0 L SOHC V6 that produced 162 hp (121 kW) and 180 lb·ft (244 N·m) of torque, also used by many previous Nissan models such as the Maxima and 300ZX. Like the 300ZX, the M30 was a front-engined and rear-wheel drive vehicle. The transmission was Nissan's RE4R01A four-speed automatic with overdrive, as enabled or disabled by a button on the shifter. There was no option of a manual transmission. The differential was a Nissan R200-type open differential. It is generally regarded among M30 enthusiasts that the change of powertrain, weak suspension and the lack of options in these categories was a mistake on Infiniti’s part, and perhaps to blame for the lackluster sales. The M30 (coupe) weighed about 3300 lbs (1498 kg), and produced 162 hp (121 kW). The M30 convertible weighed approximately 200 lbs. more, due to body and chassis reinforcements.
The M30 was equipped with the Nissan Sonar Suspension II system that was also installed on the Maxima at the time, which featured a sonar module mounted under the front bumper that scanned the road surface and adjusted the suspension accordingly via actuators mounted on the strut towers. There was also a switch on the center console that allowed the driver to change between "Sport" and "Comfort" settings—essentially "firm" and "soft", respectively.
For 1991 and onwards, the M30 received only minor improvements. If the exterior driver's side door handle of the coupe was pulled while the doors were locked, the keyhole would illuminate and the interior dome light would come on. There was also an available central locking switch placed next to the Sonar Suspension II adjuster, although it is not known whether this was a standard feature or option for 1991-1992 models. Main gauge cluster text was changed to match the rest of the Infiniti lineup, and engine oil temperature and fuel gauges were switched around. The speedometer was also changed to an electric-type, as opposed to the cable-type used on the 1990 model.
The M30 convertible was the sole convertible of the Infiniti line, until the G37 convertible's introduction in 2009. Infiniti selected about half of the models produced from 1991 to 1992 and converted them to soft-top convertibles thorugh the ASC (American Sunroof Corporation). Convertible tops were fully automatic, requiring the driver only to push the up or down buttons to the left of the steering wheel (which replaced the rear defogger button found in the coupe) to raise or lower the top.
While the power tops on these did not necessarily need extensive maintenance, they could be operated manually if necessary. All M30 coupes had power tilting/sliding sunroofs standard, with "auto-cut" while sliding to the closed position to prevent anything from getting caught by the glass.
The M30’s production run lasted for only 3 years, ending in 1992 due to lagging sales. It is not known exactly how many models were produced, but it has been said that just over 12,000 were made, half coupes, half convertibles, making the M30 the rarest Infiniti ever put into production. Previously rumored by M30 enthusiasts was that only 5,000 were made in total, half being coupes and half convertibles. Speculation regarding the exact production numbers for the M30 are, however, still uncertain. The M30 was replaced by the Infiniti J30, a mid-size 4-door sedan. While the J30 is a completely different car and has a different chassis code (Y32), it was called the "Leopard J. Ferie" in Japan and was still referred to as the Nissan Leopard.
The M30 came with a driver's airbag and ABS (anti-lock brakes) as standard equipment, though it lacked belt pretensioners, and had no rollover protection on the convertible. All M30s came with 3-point self-locking seatbelts located at each outer seat, and the rear-center seat had an adjustable lapbelt.
The M30 received 4 in both frontal- and side-impact crash test ratings according to the NHTSA, making it one of the safest cars in its class. Nissan paid special attention to the placement of the M30's side reinforcing, which is located most notably in the doors and quarter-panels. The M30 is known to have a remarkably solid chassis in coupe form.
The M30 has a small cult following, similar to that of the Nissan Leopard F31 built in Japan. The car shares many similarities with more successful and capable Nissan sports cars, such as the 240SX, 300ZX and early-generation Skylines. As such, more powerful engines, manual transmissions, suspensions and limited slip differentials from these cars can be swapped into the M30 to create a much more capable car. In both the U.S. and Japan, the M30/Leopard has been used for drifting, as it can take parts from other Nissans and is rear-wheel drive.