The new 3.6-liter H6 engine replaces the previous 3.0-liter H6, yet features the same external dimensions thanks primarily to a unique shortened connecting rod design. As a result, this larger-displacement and more powerful engine maintains its excellent low center of gravity. The 3.6 Boxer engine produces 256 horsepower and 247 lb.-ft. of peak torque, compared to 245 hp and 215 lb.-ft. of torque for the previous 3.0-liter engine. Active Valve Control System (AVCS) variable valve timing on both the intake and exhaust valves optimizes power delivery across the engine's speed range while helping to reduce emissions.

Not only does the 3.6 engine offer greater performance than the previous 3.0-liter unit, but does so using regular-grade fuel compared to premium required in the 3.0. The specially tuned five-speed automatic transmission, combined with the greater torque output of the new engine, helps make the Subaru Legacy 3.6R models more responsive when driving in hilly areas by significantly reducing "hunting" between gears.