For 2008, Volvo added the T6 as the S80's midlevel trim, between the 3.2 and the V8. The T6 features a turbocharged 3.0-liter, 281-hp inline-six engine with a six-speed automatic transmission. Gas mileage comes out to 15 mpg in the city, 23 on the highway. Drivers like the power in this V8-like new trim.