The 1972 Citroën SM was one of many innovative models produced by the French automaker over the decades. What set the SM apart, according to Jay Leno, who has owned this particular car for 35 years, was its engine. He gives the details in this episode of Jay Leno's Garage.

Other notable Citroën models like the Traction Avant, 2CV, and DS had notable technical innovations, but their engines were nothing special, Jay says. But when Citroën started planning the SM, which was intended to be the automaker's luxury flagship, engineers decided that they needed something special under the hood.

That something was a 2.7-liter, quad-cam V-6 developed by Maserati, which Citroën took control of in 1968 (the two automakers parted ways in 1975). It sent about 170 horsepower to the front wheels through a 5-speed manual transmission (an automatic was available as well). The SM was actually the fastest front-wheel drive production car of its time, with a top speed of around 140 mph, according to Jay, though he notes acceleration is leisurely.

1972 Citroën SM on Jay Leno's Garage

1972 Citroën SM on Jay Leno's Garage

Citroën was at the forefront of engineering, and the SM was a clear example with its hydro-pneumatic suspension system. Jay says it provided such a smooth ride that Rolls-Royce licensed it. The system could even jack up or drop the ride height while stationary, allowing for tire changes without a jack. The power steering and brakes used the same hydraulic circuitry as the suspension, making this system as complex as it was effective. The car's brake pedal is a round button that looks like a mushroom, and the front discs are located inboard, as we can see when Jay puts the car up on a lift.

The SM's style takes on the futuristic look that made Citroën so progressive. A drag coefficient of 0.26 was very sleek for the time (and even now), and the lack of wind resistance while coasting is noticeable, Jay says. His car also has European-market swiveling headlights, which were not legal in the United States in 1972.

As usual, Jay takes the car out on the road later in the video. Jay notes that the car is a pleasure to drive, and we can hear that the V-6 has a pretty nice wail.

Watch the full video for a detailed look at this 1972 Citroën SM. If Citroën's are your thing, check out the Jay Leno's Garage episode featuring a 1949 Traction Avant.