How the Volkswagen Diesel Scandal Will Affect Your TDI's MPG Rating | Edmunds

How the Volkswagen Diesel Scandal Will Affect Your TDI's MPG Rating


SANTA MONICA, California Volkswagen owners are reeling from the shock of the VW emissions crisis that came to light last week, as the Environmental Protection Agency (EPA) investigation exposed a scandal involving 11 million VW diesel vehicles worldwide.

As we wait for more information, and likely an official recall announcement, consumers are now left to consider several things, including how will this affect fuel economy ratings for Volkswagen TDI cars.

According to Edmunds Director of Vehicle Testing Dan Edmunds, Volkswagen TDI vehicles will likely get closer to their advertised EPA mileage estimates once a fix has been instituted.

The illegal software installed by Volkswagen allowed the affected TDI vehicles to routinely exceed the fuel mileage numbers on their window stickers.

We observed this firsthand during our yearlong test of a 2013 Volkswagen Passat TDI. Its window sticker said it would return 34 mpg in combined driving, yet we averaged 37.2 mpg after more than 20,000 miles. We were a little surprised then, but now the exceptional fuel economy makes more sense.

The difference is a result of the way Volkswagen was bypassing U.S. emissions tests. It did so by equipping some of its diesel cars with two different engine settings. The cleaner of the two settings would engage when the car's engine control computer sensed that it was undergoing an emissions test. But in all other driving situations, the computer would use a second setting that improved performance but increased emissions.

What most consumers may not realize is that the EPA derives its fuel economy numbers from the amount of emissions a vehicle emits. So in the case of the affected VW cars, their EPA mileage numbers resulted from the cleaner of the two computer settings, and therefore won't change much once a fix is implemented.

Edmunds says: After the fix, your TDI is likely to achieve the fuel economy the EPA reported on your VW's original window sticker, although it might not feel as peppy as it did before.

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