Join Date: Feb 2009
Car Year: 98
Car Model: GM67 + 03 SG
Feedback Score: 2 reviews
The "wind resistance" the mudflaps create will not diminish your mileage by any noticeable amount. We already drive toaster ovens with wheels, so "streamlined" is not a huge design feature.
Now, if a large amount of snow/ice/gunk builds up in the wheel well and rubs on the tires, that might do something to your gas mileage. But again, if you are driving in conditions where that much crap is getting stuck in the tires, gas mileage should be out the window and getting home should be the major concern.
I put some large mudflaps on my RS years ago and never saw any issues with gas mileage. I'm expecting the same with future modifications to my forester.
'03 XS Premium w/5MT
'98 2.5RS now with 100% more 5MT