The 2010 Subaru Legacy 2.5i models are powered by a revised 2.5-liter 4-cylinder Boxer engine, teamed for the first time to a new 6-speed manual transmission or the available new Lineartronic™ CVT. The CVT is standard in the Legacy 2.5i Limited, where it is also equipped with a manual mode and steering wheel paddle shifters.

The 2.5-liter engine, which is available as PZEV-certified, is modified for 2010 to improve performance, responsiveness, and economy. The engine delivers 170 horsepower @ 5,600 rpm and 170 lb.-ft. of peak torque @ 4,000 rpm. The i-Active Valve Lift System (AVLS) ensures a broad torque curve and smooth response at all engine speeds, while also helping to improve fuel efficiency. All Subaru Legacy models for 2010 feature a larger fuel tank, now 18.5 gallons vs. 16.9 gallons in the previous model, to extend driving range.

Whether teamed to the new 6-speed manual transmission or the Lineartronic™ CVT, the roomier 2010 Legacy provides quicker acceleration and lower fuel consumption than comparable 2009 Subaru Legacy models. Either transmission helps make the Subaru Legacy more responsive in everyday driving.

Subaru has adopted a chain-type CVT, the world's first longitudinally mounted CVT system for AWD production vehicles. It employs smaller pulley cores, which helps make the unit compact and can help provide better fuel efficiency compared to belt-type CVTs. Unlike a conventional automatic transmission, which uses fixed gear ratios, a CVT provides infinite variability between the highest and lowest available ratios with no discernable steps or shifts. The CVT continuously and smoothly adapts to performance demand, helping to keep the engine in its most efficient operating range.

Because a CVT does not shift gears, the driver enjoys smoother performance in all driving situations. The selectable manual mode of the Lineartronic™ CVT uses six pre-selected steps to allow the driver to "shift" manually using steering wheel paddle controls.