MPG question for smart people

So our 00 2.2L 5sp took 9.2 galllons to fill and the trip odometer read 305 miles. 33.15 mpg not too shabby (if its accurate) on 75% freeway driving. The car originally rode on 15" wheels and I am currently riding on 17's. How is this affecting my math on mpg? Thanks

 

9.2 gallons to fill the whole tank?

 

^^ you need to know the rolling circumference(or rotations per mile) of the original tires and the ones you are currently running to get your answer.

http://www.1010tires.com/tiresizecalculator.asp

http://www.miata.net/garage/tirecalc.html

 

Circumference and Weight, i believe

 

well mr foxy. no doubt you'd get 333333333.5 mpg, cause that car never seens anything over 4k rpm or 55 mph.

i will make sure i start buying all my used cars from you, cause I know they've never been beat on:biggrin:

 

Ive recently gotten as high as 31 in my Turboed 2.2 with LGT injectors....stay out of boost, and shift below 3K and you save ALOT of gas.

 

It all depends on the tire size. If you are rolling on slightly larger tires (ie 225/45/17) then you will be traveling farther per rotation of the tire and your MPGs will actually be higher. If you have a smaller tire (compare to 195/60/15 as stock) then you will get lower MPGs than what you calculated.

 

I believe I posted a while back my 06 leggy got 36.5mpg on the LCD, lol...560 miles with a full tank of gas...

 

I am running a set of stock 05 LGT wheel/tire set up 225 45 17 I believe....so actually higher mpg. wow! thanks

 

i get concerned around 300 mile mark...so i just stop and fill. I'm not sure what the tank capacity is.

 

i put over 11 gallons, i fill up about 25 miles after the light goes on

 

215/45/17

 

all legacy, outbacks are 16.9gal and imprezas are 15.9gal...

I believe all the 08 imprezas now are 16.9gal..correct me if I'm wrong.

Even if you push 400 miles (city/hwy) you still fine rick.

 

Assuming the sizes noted are correct, you are actually getting almost 2% better mileage than the number suggests. However, speedos are rarely accurate and always err on the high side. Typically a safe number to use is 5%...so you are likely running about 3% less than you reported...

 

Tire sizes aren't 100% accurate, either. The Foresters run a bit light (under speed) with the stock tires and this is often corrected with other models of tire in the same stock size. If you want to be certain of your mileage, use a GPS unit for a tank or two to get better accuracy on distance.

 

even GC chassis? Ive never been able to put that much in.

 

You are wrong. My '96 Impreza has a piddly little 13.1 gallon tank.

 

yea i dont think my tank is any bigger

 

i noticed the same to. winter setup is 205/55/16 and get 23-25mpg. when i switched to my summer set 205/40/17 i get 27mpg consistantly? iono i'm a happy camper though ;D

chingchong

 

nope, fail, 13.9

 

^^thats what i suspected