Those can't be hand calc'ed numbers unless you somehow drive downhill wherever you go. :-) I lost about 1-1.5 mpg off my hand calc'ed numbers when I went from the stock tires to 315/70 17s. The loss is about the same with the true 35" Toyos I'm running now.
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2007.5 3500 SRW 6.7L, 68RFE, PW flares, UConnect, Infinity, EZ Gate,
KORE 2.5 Stemtop Chase system with control arms, 35" Toyo M/Ts