Fuel Milage Calculation

[MorePower7701]

I am trying to calculate my fuel milage, my speedometer reads about 4MPH slow, example if my speedometer reads 45MPH I will be going close to 50MPH. I have 120 miles on my trip odometer, how would I calculate the actual milage?

Thanks

 

[cr_the_machinist]

Do a simple ratio equation to find it out....

45___120
---- = ----
49____X

X = actual millage......

Some if your trip reads 120 the you really when 130.56 miles

Just times your trip readings by 1.088 and you will get your actual millage (1.088 being your conversion constant)

 

[Rammunition360]

erase the trip, fill the tank...run some out, fill the tank, note how many gallons you used between fill ups then divide mileage by gallons factoring in your speedo diffrence...or do it like i do...run it out put a gallon in run it out haha

 

[almostclueless]

erase the trip, fill the tank...run some out, fill the tank, note how many gallons you used between fill ups then divide mileage by gallons factoring in your speedo diffrence...or do it like i do...run it out put a gallon in run it out haha

Yep, it's about gas used and distance traveled...

 

[AllanD]

Actually (45/49) X Miles will give you your correction for the speedo error

THEN Simply divide miles by fuel consumed to calculate mileage.

Alternatly you can caculate mileage first, then multiply it by your
correction factor (0.918367346) to allow for your speedo error.

Frankly I'd replace the speedo driven gear by one with one tooth less
to spin the speedo faster and make it read correctly.

AD

 

[evanesce69]

lets say he drives for 1 hour at the spedo of 45:

1) he knows the gauge is off by 4 mph slow.

2) he would actually be going 49mph for that 1 hour trip.

3) instead of going 45 miles by spedo, he is going 49 miles actual

4) lets assume he burns exactly 2 gallons of fuel in that one hour trip.

....a) the spedo mpg would be 45/2 or a 22.5mpg

....b) the actual mpg would be 49/2 or a 24.5mpg

....c) 49/45 * 22.5 = 24.5

5) it is actually the multiplier that CR said



if he figured the spedo miles, he will show a lower mpg

it only seems logical that it is 49/45 or 1.089

 

[CraigK]

The MPH shown on my speedometer are not accurate either. But, my odometer, which reads the miles traveled, is much more accurate. I've tested this by checking the odometer reading against the mile marker posts (which are marked to a tenth of a mile) located on a main interstate, and for an extended distance. Perhaps because I'm running 235x15 tires, my odometer is only about 2% off, so when doing mileage calculations, I just use the straight odometer reading.

CraigK

 

[evanesce69]

for short distances the difference is negligible. but if you were to travel large distances, say on a vacation trip where you traveled 1000+ miles, then it will make a difference in the calculations. It goes without saying that even the small numbers add up, but the steady state of the calculation is constantly changing; the style of the driving. The miles still continue to add up though.