Toastado said that his average dropped 3 miles per gallon when he went to 18's. How much did your guys mpg drop when going to 18" wheels?

 

depends on the weight of the wheels and tires as compared to stock... size of the wheels is less relevant then the weight of the wheel and tire combo, though size is a factor, more weight = more rotational mass = less MPG. if yo are really really concearned with mpg's get some ultra light weight wheels that are the same size as factory, if you want that nice 18'' wheel look, you have to make a sacrafice somewhere, but a dip in mpg can be countered with better driving habits, slow steady accl, slow breaking, coasting in gear, etc...
in my gen 1 on 18's i consistantly get about 40mpg avg, city and highway... on longs trips, i can get it up to 50ish mpg... and my wheels are pretty wide and deff heavy like a mo fo.. there are lots of options for lightweight 18 inch rims though, i am sure you can find a match that meets your needs and style

 

I'm not concerned about finding a lightweight wheel. I can certainly do that. It's just that Toastado said that he dropped 3 mpg when switching to the 18's even though he says he is using a lightweight wheel.

 

right now, I'm on 18"s and I get anywhere between 27-30MPG on the freeway, but I usually driving aorund 60-65 MPH as well.

 

What tire size is he running?? Is he compensating in his calculations for any speedo difference induced by different overall tire diameter?? Perhaps he doesn't really have a 3 MPG decrease.../shrug?

 

I don't know.

 

I have 18s as well, running 235/40 Yoko's S-Drive. I don't know how much it drops because I put them on first thing when I got my car. I got 24 mpg avg at first but after it breaks in w/ light throttle driving style, I can get around avg 27 mpg.

 

That's not bad

 

I also run 215/40/18's. They are roughly 4% too large in diameter so they record 4% less miles than I actually travel since the odometer registers X miles per X tire revolutions and my bigger tires go 4% farther per revolution. Therefore 100 miles =105 miles actual. 4% is enough difference to account for about 1.2 MPG based on a 30 MPG average. I saw about a 1.5-2 MPG drop in my actual mileage (after taking the 4% difference in to account) when I put the 18's on. I also installed amps and a heavy speaker box at the same time as well as a layer of sound deadner sheet all over the inside of the body. I account for the MPG change due to weight of the above as well as higher rolling resistance of the wider tires with more aggressive tread. I still get 26-27 MPG in town in mostly stop and go traffic (except when I run the A/C...for A/C subtract another 2-3 MPG).