Much better than any mid-size in the past--think back to the drinky turbo T-Types--today's Buick Regal sedan doesn't quite reach the gas-mileage heights of larger, mass-market four-doors.
Now that last year's base four-cylinder is gone, the eAssist mild hybrid drivetrain becomes the entry-level Regal configuration. It has some of the components of a hybrid, and it's classified by the EPA as a hybrid -- but GM prefers to dial down the "hybrid" for its marketing, since eAssist is a bit more limited than full hybrid vehicles. The variation on hybrid technology uses lithium-ion batteries and motors to boost acceleration under heavy power demand, and to run accessories such as air conditioning, but the Regal can't run on electric power alone.
With eAssist teamed to its four-cylinder and six-speed automatic, the base Regal is rated at 25/36 mpg by the EPA. That's not much higher than the base gas-only Hyundai Sonata and Kia Optima, or the EcoBoost 1.6-liter Ford Fusion--and it falls well behind the 38-mpg highway registered by the Nissan Altima.Opt for a turbocharged Regal, and mileage slumps, with either the automatic or the manual transmission. The Regal with the 220-horsepower, 2.0-liter four earns a 20/32 mpg rating when paired with a manual transmission, or 18/29 mpg with the automatic. The Regal GS, with its additional power, is a bit lower, at 19/27 mpg for the manual-shift model and for automatic versions.