The Official Superchips Forum

Hey all, looking for the best bang for the buck in terms of gas mileage. I have a 2008 Yukon XL with the 5.3 liter flex fuel engine. I have installed a K&N CAI and Magnaflow Cat back.

So the question is, which tune would be best from an overall cost standpoint with respect to mileage? The 87 or 91 octane? what are the mileage increases? One thing to note, premium gas up here in Canada would run an extra 40 cents a gallon.

I would run a full tank of both just to check mileage. Check you mpg on both anf then your cost per gallon. I break about even with an '07 silverado VMax, if I can keep my foot out of it, which I can't...

I believe on all of the 5.3L motors in the Yukons we make a decent amount of power on the 87 tunes, to help with fuel. The 91 octane output is so close that it would not warrant running the higher tune.

Ron

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