I suppose none of us in the peanut gallery know for sure. Knowing that they battle for 1 mile per gallon on their fuel economy ratings, my guess is that it's a

I suppose none of us in the peanut gallery know for sure. Knowing that they battle for 1 mile per gallon on their fuel economy ratings, my guess is that it's a minor effect for a car owner, but a major effect on VW's marketing. I read elsewhere that their technique for cleaning the exhaust can gunk up the filter more quickly too, so it might also change the maintenance schedule. Which, again, may not really be a huge issue for a car owner, but could impact VW.