The Buick Regal gets more adept at using less fuel this year, in turbocharged versions, at least. It's still behind the benchmarks set by some larger mid-size cars, particularly when the mild-hybrid eAssist model is put into context.
The eAssist had been the base Regal since the 2012 model year, when Buick dropped its non-turbo, non-hybrid standard engine. This year, a less-expensive version of the turbo supplants it as the entry-level Regal. The eAssist combines lithium-ion batteries and motors to boost acceleration when the Regal accelerates—in tandem with a larger-displacement four-cylinder engine—but it's a bit more limited in scope and intent than a true hybrid. The Regal eAssist can't run on electric power alone, for example.
As a result, its EPA gas-mileage ratings of 25/36 mpg, or 29 mpg combined, aren't in the same league as the Ford Fusion Hybrid's 47/47-mpg rating, or the new Honda Accord Hybrid's 47-mpg combined rating. In fact, it's not much more than the non-hybrid 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's turbo 2.0-liter four earns a 20/31-mpg rating when paired with a manual transmission, or 21/30 mpg with the automatic. With newly available all-wheel drive, the Regal is rated a bit lower, at 19/27 mpg, or 22 mpg combined. Conclusion Gas mileage—even in the eAssist mild-hybrid Regal—isn't the best, but the new turbo four does a little better.