With substantial weight savings and all-new drivetrains, the seventh-generation 2015 Volkswagen Golf TDI -- coming to the U.S. next year as a 2.0-litre TDI model, and also a hot hatch Golf GTD -- suggests diesel fans may get the kind of fuel-efficiency figures normally reserved for hybrid cars.
But half a world away in Europe, Volkswagen makes an even higher-mpg diesel we’ll never see here: the Volkswagen Golf BlueMotion.
In Amsterdam last week testing the all-new Golf Variant wagon (due in the U.S. as the 2015 Jetta Sportwagen), we used the opportunity to put Volkswagen’s latest high-mileage forbidden fruit through its paces.
Smaller engine, clever tech
Unlike Volkswagen’s standard 2.0-litre four-cylinder TDI in the U.S. market, the Golf Bluemotion uses an all-new 1.6-liter, 110-horsepower, four-cylinder TDI engine that VW says has been built from the ground up to offer maximum torque (184 pound-feet) from just 1500 RPM.
Paired to a six-speed, low-friction manual transmission with taller gears than the rest of the Golf range, VW says the Golf Bluemotion can cruise at freeway speeds using the engine’s most efficient power range -- between 1,500 and 3,000 RPM.
There’s more. Because internal-combustion engines are least efficient and most polluting when warming up, VW engineers have worked hard to ensure the Golf Bluemotion’s 1.6-liter engine warms up as quickly as possible.
It uses separate cooling-circulation loops for the cylinder head and the crankcase, as well as an electronically-operated water pump that can be switched on as needed to speed engine warm-up times.
In addition, exhaust gas recirculation cuts oxygen in the pre-combustion mixture, dramatically reducing the amount of NOx emitted in the exhaust.
Other tweaks too
Improvements to Golf Bluemotion fuel efficiency go beyond its new engine, however.
By lowering the car an additional six-tenths of an inch over the standard Golf, adding a specially-designed rear spoiler, and fitting a unique grille that forces most of the air hitting it over the car rather than into the engine bay, the Golf Bluemotion has a drag coefficient of 0.27. The standard seventh-generation Golf, for reference, has a Cd of 0.28.
As for wheels? As you’d expect, wheel options for the Golf Bluemotion are functional first, with a choice of 15- or 16-inch alloy wheels fitted with Michelin EnergySaver low rolling-resistance tires as standard.
Unlike other models, there’s no spare: while there’s still space for a spare under the load bay floor, the wheel and tire itself is sacrificed at the altar of fuel economy.