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Old 06-02-2012, 12:02 AM   #44
serialk11r
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Garage
Quote:
Originally Posted by Mitch View Post
Base mpg: 30.0 mile / gal
New diff: 5% improvement
New mpg: 31.5 mile / gal

Premium fuel cost: $4.00 / gal

Base gas cost: $0.133 / mile
New gas cost: $0.127 / mile
Savings: $0.00635 / mile

Payback mileage (miles to break even, every mile after is actual savings): 157.5 miles per $1 spent modifying the gear ratio.
In other words, if you spend the $1106 mentioned earlier, it would take 174,195 miles before you broke even on the cost of the differential.
Yes, which is why the cost needs to be taken into account obviously. If it weren't so expensive to get custom gearsets made then a 6th gear swap that drops revs say 15-20% rather than just 10 would make a lot more sense.
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