My math was all wrong .... so I was getting 274 miles on a tank of gas.
Well, if my speedometer was not accurate with my tire size, then I was using bad data.
speedometer @ 60mph (if calibrated)
revs per mile - 761.6
Patriot Wheel: 215/65/17
speedometer @ 58.5 - 2.53% slower
revs per mile - 742.8
New tires: 245/65/17
speedometer @ 55.4 - 8.135% slower
revs per mile - 704.3
So using my GPS which should be the same accuracy irregardless of the tires/wheel size. When it shows me doing 60 and my speedometer shows me only doing 55 mph, I figure that I have driven about 5 miles per hour further than the odometer is showing. So at the end of a tank, lets say 5 hours driving @ 60 mph average, my odometer would be 25 miles less than I actually traveled.
This might be hard to follow, I am not good at explaining things
So let's say I did 275 miles on that fill up and it was 12 gallons. That is 22.9 mpg ... but wait, it should really be 300 miles and 25 mpg .... right??
Why does this even matter? I have no idea ... it is just one of those things that I have been thinking about all night for some stupid reason.
'07 Compass Limited 4X4: K&N Air charger, Borla cat back exhaust, Rocky Road Lift kit, Firestone Destination A/T 245/65/17's, Red painted brake calipers, Pioneer AVIC Z2, Sirius, iPod interface, Polk Audio 6X9s (all 4 doors), Polk Audio Tweeters (dash), Polk Audio 6.5s (rear hatch), 2 Kicker CVR 10" Sub woofers in custom enclosure (hidden), Eclipse XA4000 4 channel & XA1000 1 channel amplifiers.
Peep my ride: http://www.cardomain.com/ride/3031696