I think weight will be the biggest factor. I've done a lot of research on my stock 03 wheel setup, as I'm about to replace both wheel and tire.

Stock 03 HCH wheel is ~ 15lbs. I say "about" because Honda was unable/unwilling to part with the actual number. I found the 15 lb value on an after-market web site about 4 months ago but I cannot find anymore.

Stock Dunlop SP 20 FE 185/70R14 is 17.6 lbs (from Dunlop).

Total whell setup is 32.6 lbs.

I've read that 1 lb of unsprung wheel weight (weight of your wheels) is equal to about 8 lbs in the car. So cut your wheel weight by 4 lbs and you're "carrying" about 32 lbs less in the car. All research I've found said that reduced wheel weight will help FE, but none say by how much. Conversely, none will quantify how a heavier setup will hurt.

You should be able to research what that Civic EX setup weighs. Most web-sites selling tires will include wheel weights, as will most manufacturer web sites as well (however, I had to call Dunlop because the SP20 FE is not generally available on the web, but you can buy it at certain tire stores). Then, you can get a better feel for whether you're going up or down.

I'll mention that finding a 14" or 15" wheel under 15 lbs is not impossible, but the choices are few. I found two 15" wheels I considered - each at 10.3 and 10.7 lbs. The first was the Motegi Track Lite 2 (silver). Was my first choice but Motegi is currently out and they don't know when they'll make more (astounding, but true). I'm going with my second choice of the OZ Superleggera. Also watch out for tires. I'm looking at 195/60R15, and the lowest weight I've found is 18.3 lbs. Some are as high as 21 or 22 in that size.

I know that's a lot of detal - maybe more than you wanted or needed. You may want to make sure of the wieght of yor EX wheel before making a change. The stock setup is pretty light. A 15-16 lb wheel is considered "very light weight", which begs the question, what is "normal". A heavier setup will reduce your FE, but by how much I don't know.

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