I recently got some 17 inch drifz wheels with 245/15/17 tires on them. after that I purchased one of those universal mufflers off ebay. I recently noticed a significant decrease in my gas mlg after purchasing both products. I used to go 200 miles and be at half a tank of gas, and 400 when I was empty. Now i am down to 275 miles on my civic and its empty. Could these products have something to do with with decrease or could it be something else....PLZ HELP!

 

I'm assuming you have an 89 civic based on your forum name. I'd say that its the 17 inch wheels. if I were you I would sell those and get some 15's with a 50-55 percent tire wall. for instance. 15 inch wheel with a tire size of 205/50-15 older civics weren't meant to have 17's. you may not like the wheel gap, but id do that and put a set of coilovers and lower it a little.

 

Actually I have a 2000 Honda Civic Ex coupe...Would you still consider the same scenario?

 

what was the original wheel size?

 

Need to know the actual new tire size. Never seen a 245/15/17. Check the middle number.
Stock tire was 185/65/14. (although I am sure there were optional sizes available that would translate to the same diameter) Aceptable 17" replacements are
195/40-17
195/45-17
205/40-17
215/40-17

 

I apologize the tires size is 215/45/17...that was my typo. I am not sure of the regular size I believe the org. alloy were 15 inches

 

The new tire will cause your speedo to be 4.9% too slow. This means when your speedo shows 60 you are traveling at 62.9. This will show as a decrease in your mileage but not nearly the amount you are talking.
You could be running winter gas which reduces the mileage, but I suspect your driving style may have changed with the new muffler as you probably like the use the skinny pedal more to hear it.
There are many other places to look though, air filter, plugs, cap, rotor, O2 sensors etc.

 

"winter gas"? WTF? Is that on the same shelf as blinker fluid and winter air for your tires?

The decrease in mileage is caused by those huge rims. I made the mistake of putting 17s on my 2000 LX. It was a bad idea. It took longer to accelerate. It took longer to brake. Speedo was off. True gas mileage went down. If you truly care about your gas mileage, go to a 15 inch rim, max. 205/50/15 tire, max.

 

I will check the plugs and air filter tomorrow, But if anything I guess I will have to go with smaller wheels. It's weird when I first put the wheels on everything was fine, but after I put on this muffler off ebay thats when it really changed, but everyone has said it cant be the muffler so I am not sure...

 

http://auto.howstuffworks.com/fuel-e...mmer-fuel1.htm

http://ask.cars.com/2009/02/whats-th...y-cars-pe.html

Need more info??