MPG ?

[divad82]

Well I was averaging 23 mpg's with my stock 17' rims and recently installed 19' rims and guess what, my mpg dropped to 17 mpg's. What the heck, I expected to lose maybe 1 or 2 mpg's but not 5. Has anybody else seen a big drop in mpg's as I did. Is this normal.

 

[jpplaw]

Are the tires the same circumfrence? Turning more RPM?

 

[racerraj]

Does the car feel sluggish on acceleration?

 

[divad82]

I can't remember but I think the tires are 245/50/19 but they are stock 2010 wheels/rims. And the car doesn't feel like it accelerates as it should. Anymore thoughts.

 

[racerraj]

Did the wheels and tires feel that much heavier? Hard to imagine it would make that much difference. Check the air pressure. With the shorter stiffer sidewalls maybe it wouldn't look as low on iar even when it is. Try near max rated pressure and see if that helps.

If the diameter is different from factory, it will register miles wrong. Depending on which way it could show you losing mileage even if you really aren't. Are you making the same drives and still adding gas at the same time? If so maybe it isn't off by so much, just saying it is.

Borrow a GPS and compare the speed it says to what your speedo says.

 

[NotQuik]

I've gotten 29.5 mpg with the heavy 20's in my sig and 31.0 with stock 18" bullitts before. Something doesn't sound right.

 

[racerraj]

29.5 with the 4.10's? That's good. What speed. 31 is my max Cruising at about 68mpg with 3.55s.

Approx 2mpg is the most I would expect to lose going to 20's. Even that is a lot.

 

[jmuva44]

Gas mileage is primarily dependent on the driver. If you dropped 5 MPG then it sounds like you are breaking in the tires.

 

[mustangsquared]

crap, I have a totaly stock 06 GT and only get 24mpg... 25.6mpg with the cruise set at 70mph and driving the entire tank on the highway and I only have the stcok 18's on stock tires! What am I missing??

 

[SpartaPerformance]

Bigger wheel mean more reciprocating mass, less MPG especially if they weigh more then factory.