Found some Si wheels locally with good tires for sale. Will it change my MPG on my 99 LX going from the 14" steelies to the Si wheels? I wouldnt think it would do much difference from 14" steel to 15" aluminum..

Please advise if anyone has gone to this setup.

thanks!

 

I don't even know why you would be concerned. If there is a difference it would be negligible. If you're worried then don't install them.

 

^^^ I agree LOL If it did decrease your MPG it would be barely noticeable.

 

I saw a 3-5mpg decrease in switching from 14" steelies to 15" GSR wheels on my 1999 civic Lx sedan. There is a huge mathematical equation for this, but you are increasing rotational inertia, rolling mass and rolling resistance, so YES it will effect your fuel economy, as stated and proven above

Edit: as well as the increased wear on your brakes, I went back to the 14" steelies after 1 month as this is my DD.

 

Another thing to keep in mind is that going to a different tire size affects your speedo, which can throw off your mpg calculations. Once you factor in the tire diameter, you may find an increase in mpg vs what the odometer says (and vice versa.)

There's a good tire size calculator here.

 

Thanks bro for a straight forward and helpful answer as requested instead of a sarcastic one!! Great info to consider

Thanks again