I did a quick search and I couldn't find much on this topic. i currently have the 20" OEM wheels on my EL and I have been thinking about switching to 18's just to get a better tire selection and maybe pick up some lost power and MPG's in the process. I would think that there would be less unsprung weight going to a smaller wheel, but that might be made up in more rubber in the tire. Has anyone done this or maybe at least done some math on possible weight savings?
I have 18's on my 07 Limited from the 20" OEM wheels. The rubber is within .20" in total circumference between the two. The increased sidewall, in my opinion, makes the vehicle ride sooooo much better. As for fuel economy, I get no difference. As for looks, about the same, less flashy, which I like. I have 18" OEM wheels from an F150 from 2008, or so.