I have a 2004.5 Duramax LLY, 4WD,SB,Crew Cab, 36,000 Miles+. Does anyone know how GM calculates mileage for the DIC? When using a Predator tune, it throws my mileage calculations way off; 25%-38% higher indications than actual. Diablo can't or won't help. I would have thought that the mileage would have been calculated on simple fuel flow minus return, but apparently not. Must be calculated on volume predicted or some such thing that Diablo messes with. Anyone know the method GM uses? Any way to solve the problem?:)

moving to LLY electronics.. if you search through here you'll see that all tuners/programmers throw off the readings for mileage. You must calculate by hand. In the future make sure you post in the correct sections for best exposure and feedback.

Thanks for pointing me in the right direction.