Well I know the title is worrying a few of you but never fear I'm talking about tires and wheels.

I have a 2005 E320 CDI that I am always trying to squeeze one more mile per gallon out of and I initially had 19" Brabus Mono VI style wheels on the car (like my icon) (P245/35R 19). They grip the road and the curves like a errrrrr (BMW) but anyway, apparently they were robbing me of about a 10% reduction in mpg. If you read any of my other posts I am always comparing what others get on the CDI's and Bluetec's I was getting around 29 to 30 mpg with the 19" wheels.

Well as luck or unluckiness would have it I had a flat and ruined one of the wheels so I put the stock 16" wheels back on all the way around. I have been driving with the stock wheels for about a month (too lazy to call tire rack) and this morning on my commute I got 34 mpg (normal driving / same route).

I have noticed after changing the wheels that my increase was at least 5% and normally 10% better so yes fellas SIZE MATTER's.

 

I dont think its size so much, but weight. If you went to 19's having the rite tire size, they should be the same height as the 16's. I went from 17's to 18's on my 04 230 SS and lost 10-20% of mileage. Both sets of tires are exactly the same height. Weight is the killer

 

I would agree...it's definitely more weight than size of tire/rim.