Calculating fuel mileage

[Tinney]

So I have an older vehicle that does not show your average mpg, so I typically fill up, reset my trip odometer, drive until next fill up, then divide the miles by how many gallons I put in. Not perfect but it gives a a ballpark.

I recently swapped to larger wheels and tires so now my speedometer is off by roughy 5mph(for example it shows 55 when I’m actually going 60) because I’m now traveling farther with each rotation than my vehicle realizes. I question is: what variable would I add to account for the extra miles so I can continue to monitor my average Mpg? Thanks

 

[blamocur]

Just like you speed has to be multiplied by [imath]\frac{12}{11} \approx 1.091[/imath] to get the real value your distance, and thus you MPG as well, has to be multiplied by the same amount.

 

[Steven G]

This is what blamocur is saying worded differently.

Every 55 miles your odometer reads, you are going 60 miles.
So simply find out how many 55 miles you went (think division) and multiply this number by 60.

 

[Tinney]

Okay so if I understand correctly, my trip odometer was 220, and I put 14 gallons in the tank, 220 divided by 55 is 4, times 60 is 240. Divide 240 by 14 and I get just over 17mpg. Would that be accurate?

 

[blamocur]

Just like you speed has to be multiplied by [imath]\frac{12}{11} \approx 1.091[/imath] to get the real value your distance, and thus you MPG as well, has to be multiplied by the same amount.

Just realized some punctuation is missing in my post. Should read "...to get the real value. Your distance, and thus you MPG...". Sorry for this sloppiness.