What Happens to HP and MPG When You “fix” a VW Diesel?

Ever since Volkswagen admitted to installing an emissions test “cheat mode” into nearly half a million US cars (and more than eleven million vehicles worldwide), people have focused on the massive corporate losses and ongoing criminal investigations of VW executives and engineers. One thing that’s been talked about, but hasn’t really been settled, is the basic question every one of the affected VW diesel owner is asking themselves: how will my car perform once it’s “fixed”?

That’s what Consumer Reports set out to answer. To do so, they fired up a pair of VW diesel Jettas in “cheat mode” and subjected it to CR’s usual battery of tests. They did that by disabling the car’s rear wheel speed sensors. The “hack” meant that the car couldn’t determine if the rear wheels were spinning or not, and- consequently- whether or not the car was on a dyno. It’s a smart play by CR, but for Volkswagen? Let’s just say that the results of their real-world “cheat mode” testing won’t exactly do much to help Volkswagen win friends and influence people.

In CR’s controlled testing, acceleration suffered by a few tenths, showing that horsepower isn’t hugely affected at the low RPM. The biggest difference, then, was in fuel economy. Fuel economy dropped between 3 and 4 MPG in different testing modes. That may not sound Earth-shattering on its own, but it’s more than 40 miles less driving per tank, every tank, and that adds up over each of the eleven million VW diesel cars!

You can check out the full test results in the video, above, and let us know what you think about the VW diesel dilemma in the comments, below.

Source: Consumer Reports.

Jo Borrás

I've been in the auto industry 1997, and write for a number of blogs in the IM network. You can also find me on Twitter, at my Volvo fansite, out on two wheels, or chasing my kids around Oak Park, IL.