Not again.

 

^ Haha that damn bug in your signature gets me every time.

Thread Fail.

 

I had a really good hamburger tonight.

 

 

Its a simple calculation. Miles/gallons = MPG.

Miles are on your trip odometer, and gallons are on the gas pump.

bill

 

Larger wheels = greater circumference = more distance traveled per wheel revolution. This means your speedometer/odometer is off and you're actually traveling further than your odometer indicates. If mpg = miles/gallon then your now false numerator is giving you a false lower result. Your gas mileage didn't change, but your calculation needs to be adjusted for the larger tires. Nothing to do with rotational inertia of the wheels. Whenever changing wheel size you should have your speedometer re-calibrated. Then you could trust your speedo and your gas mileage would be calculated normally.

 

350-375 mi per tank
normally runnin 21-22 mpg city driving
i fill up about 16-17 gal each time

those are all averages i know they dont check out

 

how exactly do you get your speedometer re-calibrated?

 

First when I got my car, I used to get 16~17mpg. after any mods, mpg drops a bit cuz I tend to drive it harder but MPG keep increasing with the time I spend with my car.
now, I get 350miles+ between fill ups and I usually put 17~18Gals

 

i think i beat everyone! mostly highway to work but i avg 27 mpg,and never get less than 450 miles out of a tank,then refill is 17.8 gallons! last tank i pulled into the gas station for a refill at 498 miles to the tank damn i wanted 500 but i had been driving on ----dTE for 2 days

 

There's speedometer shops or other performance shops that do it. They calibrate the tire size to the speedometer input and change the speedometer pinion gear to match on mechanical speedometers or they change settings (dipswitches I think) in the electrical speedometers to accomplish the same thing.

 

I just got done on a 8 day 3200 mile roadtrip through the Rockies in an 04 roadster 6 speed. I hardly every touched the brakes driving through the mountains using gears for brakes. Top was down 30% of the time with the a/c on. I averaged 25.8 miles per gallon on the whole trip with the car loaded with weight as luggage. I was very impressed.

 

22 MPG mixed driving calculated the old fashioned way. Miles on trip meter divided by the gallons it took to fill back up. I wouldn't rely on the guage calcualtion as it changes all the time and is only accurate at that instance you look at it, running avg...

 

400-420 to the tank around 26-28mpg

 

Nope, not correct.

What it displays is the cumulative average since the last reset.

If you reset it at each fillup, like i do, the reading when you stop for the next fill will be the MPG for that tankfull.

And when I do the manual calculation, the number displayed is always within a few tenths of the number I calculate.

bill