One of the biggest complaints TheCarConnection.com noticed about previous versions of the Mercury Mariner is that they were woefully underpowered and generally didn't perform very well. The 2009 Mercury Mariner is vastly improved in this area, with the twin benefits of better acceleration and increased fuel efficiency.
The 2009 Mercury Mariner lineup comes with two available engines. Car and Driver says, for 2009, the "base engine, an inline-four, [grows] from 2.3 liters to 2.5" and that "power increases from 153 horsepower to 171," while at the same time "a power upgrade―to the tune of 40 horsepower, for a total of 240―also has been bestowed on the 3.0-liter V-6." Initial reviews of these two new powerplants are glowing, with ConsumerGuide reporting that the four-cylinder "provides better than expected acceleration, even with AWD." Car and Driver adds that the power increase for the Mercury Mariner "chops 1.7 seconds from its 0-to-60 time, which now stands at 10.4 seconds." Motor Trend notes a similar improvement for the V-6-powered 2009 Mercury Mariner, which offers "a 0-60-mph time that Ford claims is a substantial 1.7 sec quicker than the 2008 model." Cars.com also observes that "the revamped V-6 launches you swiftly, coming on strong particularly in the 40-60 mph range."
One reason for the improved performance of both engines, aside from the obvious power boost, is the new transmission that puts the power to the wheels. Edmunds says "both engines are mated to a six-speed automatic transmission," and reviewers just can't get enough of it. ConsumerGuide states that "the transmission shifts smoothly and kicks down quickly for more power," while Cars.com adds that "its highway responsiveness is just as good—and it has shorter gears for quicker passing-lane bursts, with none of the old drivetrain's droning exhaust." The Mercury Mariner can also tow a respectable amount with its new engine/transmission combination, and Edmunds reports that, "properly equipped, the V6 Mariner can tow up to 3,500 pounds."
As mentioned earlier, the extra power in the 2009 Mercury Mariner comes at no extra cost in terms of fuel consumption. In fact, fuel economy is "2 mpg better on the highway" for the V-6 (compared to last year), according to Cars.com. For the front-wheel-drive versions, the EPA estimates that the four-cylinder will get 20 mpg city and 28 on the highway, while the V-6 offers 2 mpg less than the four-cylinder.
Other aspects of the 2009 Mercury Mariner's performance have improved as well, with the notable exception of braking. Cars.com says "the suspension has been retuned for better handling, with a newly incorporated rear stabilizer bar." ConsumerGuide definitely notices the difference, remarking that handling is "a surprise given the age of Mariner's basic platform" and noting that "body lean in turns is well controlled, though the steering feels overboosted and vague." Unfortunately, the 2009 Mercury Mariner can't quite hold its own in the stopping department. Edmunds reviewers report "its rear brakes were downgraded to inferior drums in 2008," and for the 2009 model, it still holds true, so "the best stopping distance [they] could manage from 60 mpg was 154 feet—at least 25 feet longer than average, and frankly unacceptable."