Will putting 20 inch wheels on my S10 cause a significant drop in fuel mileage?
It really depends on your driving style. The weight of the rims is NOT going to have a significant effect on the fuel mileage. The change in final gear ratio will. If you do a lot of stop and go driving you will notice a drop in mileage. If you do mostly highway driving you could actually see a mileage increase. If your RPMs used to be 3000 at 60mph they may now be 2800 at 60mph. This will allow you to get better mileage. As to how much better mileage, I am not too sure. The best bet would be to see if you can borrow the wheels for a week and see for yourself. That way you can determine if there are any other factors such as rubbing or handling changes.
