Has anyone experienced a noticable mileage loss when going from stock to 18" rims? I just popped on some 18" TRD RH rims with the P-Zero 215/35R18 tires and it seems like the mileage dropped... anyone else & how much drop if so?

makes sense that it would happen, there is more energy required to get the wheels turning.

It could be a weight difference too. How heavy are those new rims/tires?

Yes, the added weight of the new wheels will lower your mpg.

Sorry for hijacking, but this thread is entertaining.
This forum started off as CAI but got hijacked and according to these guys, it's not possible.
I just gave up because I know from experience that it does drop MPG.

http://www.scionlife.com/forums/viewtopic.php?t=33966

the weight and the wider tires slows the car down thus making it have to work harder to continue at the same speed thus lowering mileage.

I went from stock to 17x7.5 wheels. Weight is the same but gas mileage dropped by about four, so it has to be the rolling resistance of the wider tires.

I have stock sized aftermarket rims, (15" ENKEI RPOJ-2 rims), with the original tires, and since the aftermarket rims are lighter, my mileage went up. I get around 36-40 MPG.

So, I would guess that the larger rims do make the mileage go up. Seems to make sense to me.

mileage loss is due to more rotational mass milegae in city driving will be alot lower than highway because stop.starting and extra weight needed to push.. plus when u got ur rims u prolly drive faster to show off.