Consumer Reports published results of some testing they did with a 2011 Jetta and a 2015 Golf. They used multiple drivers over the same routes. The 11 lost .7secs in 0-60 and milage went down fro 50 mph to 46. The 15 did a bit better losing only .1 sec in the acceleration and mpg dropped from 53 to 50. This is after putting to cars into test mode by disconnecting the rear wheel rotational sensors and doing some other stuff.

I figure if 50 miles per gallon is as bad as it gets I can live with it.