Come late 2014, the Volkswagen Golf, Beetle, Passat and Jetta will offer a new turbo-diesel four-cylinder engine that could get as high as 46 mpg highway in EPA figures. Final numbers are still pending, but Volkswagen announced that its new turbo-diesel four-cylinder — dubbed EA288 — will replace the existing turbo-diesel four-cylinder (shown above) in TDI versions of all four 2015 models.

Volkswagen notes that it has sold more than 47,000 diesel cars in the U.S. year to date, which represents more than three-fourths of all diesels sold here.

The engine has similarities to its predecessor — turbocharging and direct injection — and it should have the same 2.0-liter displacement, spokesman Mark Gillies told us. Beyond that, Volkswagen says it has a slew of new features, including better exhaust-gas treatment, numerous friction reductions and integration of the intercooler with the engine’s intake manifold. If that’s all Greek to you, VW says the end result should improve gas mileage and sharpen accelerator response. The new diesels also have slightly more oomph: 150 horsepower versus the outgoing TDI’s 140 hp. Torque remains the same, with a diesel-appropriate 236 pounds-feet."It’s an all-new engine, to all intents and purposes," Gillies said. "We’re hoping that it will give a probably somewhere around 8% bump to highway [fuel] economy."That could mean as high as 46 mpg in the Passat TDI, whose current EPA figures with a six-speed manual transmission are 31/43/35 mpg (city/highway/combined). That’s the most efficient of Volkswagen’s 2014 TDI four-cylinder cars; the least-efficient TDI four-cylinder, the Beetle, still gets an EPA 29/39/32 with a six-speed auto.

Unfortunately, shoppers will have to reconcile the efficiency gains — inherent because diesel fuel has more energy density than gasoline — with its higher price. A gallon of diesel averaged $3.88 nationwide today, according to AAA. That’s 17 cents more than the price of regular unleaded.

Audi, one of the Volkswagen Group’s ever-increasing umbrella of brands, will also get the engine. The brand’s current TDI cars, including the A6, A7 andA8, employ a turbo-diesel 3.0-liter V-6. But the outgoing A3 hatchback had a turbo-diesel 2.0-liter four-cylinder, and in March, Audi confirmed the car’s2015 redesign would retain an available diesel four-cylinder. Expect this to be it.