When Volkswagen finally recalls its diesel vehicles, owners may be in for a surprise once they get their vehicles “fixed.”

And the surprise isn’t the good kind either.

Consumer Reports decided to see just how much performance is impacted when diesel-powered Volkswagen vehicles are in their “cheat mode” by putting a 2011 Jetta Sportwagen TDI and 2015 Volkswagen Jetta TDI to the test. To put the vehicles into cheat mode, the publication pushed the gas pedal five times with the ignition in the on position. To avoid being kicked out of the cheat mode when the cars’ rear wheels start spinning, Consumer Reports unplugged the rear wheel speed sensors.

From there, the team ran the two vehicles through its drive cycle that involved a city traffic simulation on the track and a 65-mph highway run. Fuel economy figures were calculated by taking fuel readings from a flow meter and averaging mpg in both directions to account for grades and wind speed. The tests were also run several times in typical Consumer Reports fashion with different drivers to guarantee consistency.

The results? With the 2011 Jetta Sportwagen TDI, acceleration from 0-60 mph went from 9.9 to 10.5 seconds. The 0-60 time only slipped one-tenth for the 2015 however.

Fuel economy dropped from 50 mpg to 46 mpg while the 2015 Jetta TDI saw a loss of three mpg from 53 to 50.

It’s unclear if Volkswagen’s fix will just simply put its diesel vehicles in cheat mode at all times, although that’s very unlikely. It seems like the worst case scenario would be about a 10-percent loss in fuel economy, but until the German automaker announces a fix, nothing is definite.

This article originally appeared at AutoGuide.com