Infiniti Ms can be had with a V-6 or V-8, two-wheel or all-wheel drive, and a five-speed automatic. Either engine is more than adequate to move the M with authority. Fuel economy isn't great, though.
Edmunds calls the 2008 Infiniti M's powertrains "impressive" and writes, "the M35's V6 should provide more than enough power for most drivers." On the other hand, their editors "praised the Infiniti M45 for its explosive power." In reviews read by TheCarConnection.com, this sentiment was a common theme. Cars.com also appreciates the V-6's power, saying that it "churns out fluid power with no peaky burst or low-end sluggishness, and under hard acceleration its high-pitched whine should be music to any gearhead." Of the M45, they write, "It trades the M35's finesse for brute hang-the-tail-out power at pretty much any speed."
Kelley Blue Book provides the specifics on each Infiniti M's performance: "With 275 horsepower and 268 [lb-ft] of torque, the V6 propels an M35 from 0 to 60 in just over 6 seconds -- or slightly more for the heavier AWD M35x...Rated at 325 horsepower and 336 [lb-ft] of torque, the larger V8 in the M45 drops that interval into the mid-to-high five-second range."
Competitors in this class are adding more transmission gears than Infiniti; 2008 Ms still make do with a five-speed automatic. Car and Driver explains, "The M continues with the same five-speed automatic (although with playful rev matching). This at a time when the rest of the biz is going to six-plus-speed automatics." This is not a disadvantage, as Cars.com finds "it works just as well, if not better. It holds lower gears tenaciously at lower speeds, refusing the mileage bait of an early upshift while you're still on the gas."
Where the 2008 Infiniti Ms fall below the average is fuel economy. According to fueleconomy.gov, an M35 achieves 16 mpg city/23 mpg highway; an M35x gets 16/22 mpg; an M45 gets 16/21 mpg; and an M45x gets 14/20 mpg. In ConsumerGuide testing, "rear-drive M35s averaged 16.4 mpg. M35x models averaged 17.4-21.2 mpg with mostly highway use. Test M45s averaged 16 mpg in [mixed] driving." Premium fuel is required for the M45 and recommended for the M35.
In previous years, all-wheel drive was offered only on the M35 by Infiniti; 2008 sees the M45 available with Nissan's advanced ATTESA-E-TS (Advanced Total Traction Engineering System for All Electronic Torque Split) all-wheel-drive system. This is the same system used on the Nissan GT-R.
Underpinning the 2008 Infiniti M chassis is an "advanced suspension design [that] responds with just the right mix of compliance and firmness," finds Edmunds. "All Ms have a firm, composed ride," writes ConsumerGuide. "Base M35 and M45 absorb bumps best. M35x has tauter suspension settings, resulting in a slightly less compliant ride." Opting for the Infiniti M all-wheel-drive "X" models will "sacrifice a bit of enthusiast appeal," warns Kelley Blue Book, though "Nissan's outstanding AWD system can seamlessly transfer torque from [rear-to-front] and side-to-side as...conditions warrant, making it a feature well worth considering for those who live outside of the Sun Belt." ConsumerGuide notes, "A 50/50 front/rear power split can be locked in via the snow-mode button on the center console."
"Steering can feel a bit rough around town," writes Edmunds of the Infiniti M, while ConsumerGuide notes, "Steering feel is sporty and precise." They add, "Braking is strong." Infiniti Ms with the Sport Package receive Rear Active Steer, which "varies the geometry of the rear wheels...to deliver even more immediate and positive reactions during spirited cornering," says Kelley Blue Book. Cars.com sums it up well: "All told the steering feel encourages twisty-road driving in a way a Volvo S80 or Mercedes E-Class cannot. Body roll remains well in check, and at its limits the M displays good grip and even better balance."