curtk69

ok i did my first highway trip on a full tank of gas. it only took 18.2 litres to go 222 uncorrected kilometers.

if my stock tires are supposed to be 255/70/17 and i now run 315/70/17 whats the correction factor? i thought it was 13%

so 222x .87=182 corrected km
182 x.625 =121 miles
18.4 l divded by 4.54 =4 gallons imperial gallons = 30 mpg

thats too good to be true. even if the attendent managed to squeeze in another gallon into the filler neck[ i just let it click off] that still works out to 24 mpg. still seems to be too good to be true.

is my math way out somewhere , perhaps in the tire correction factor?
forgot to mention most of the trip was at an uncorrected speed of 115 km/h with engine rpm under 2000 most of the way.

poccnr

I average 15.4mpg and can see up to 17mpg depending on my speed on 87 octane. 3:55 gears, edge programer on level 1 (trans tune) k&n intake with a magnaflow catback exhaust. I don't go easy on it either if I did Im sure I could see close to stock numbers.

rbrais

It's not really possible to calculate the difference in %, because different tires have slightly different diameters. Get a GPS and use it each time you drive for 100 miles to a tank-full. Make sure you clear your trip when you start measuring with GPS.

See how far off your odometer is and use the GPS to calculate your MPG's. I think I was off about 30 miles per tank (250 miles +/-) when I went from 255/75R16 to 35's. Then get yourself a programmer that can correct for tire size.