[quote=Huney1]Mine has 15" wheels and I wonder if it would increase the mileage to do 16" wheels? I doubt it would be cost effective or save enough gas money to pay for the wheels? quote]
Several factors need to be considered when going with larger wheel assys.
Obviously clearance is a concern. However, one thing many miss is the increased rolling resistance that occurs with larger tires & wheels.
Years ago when most cars were overpowered larger wheels &/or tires or a differential ratio change was an easy way to gain mileage and is one I did many times. However, in todays cars where body shapes "aerodynamics" and even the way a car sits in relationship to the highway will be effected.
As you mentioned too, cost versus return over a given set of miles has to be considered. 50K miles is probably a good mileage target to look at when considering the cost of a larger diameter wheel assy. versus any expected returns.
I could type pages of issues as I've done several changes with many cars over the years but these are the initial areas of consideration.