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Why such big diff from diesel DIC mpg & hand calculation?
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Babyhauler
I have had 04 2500HD Duramax diesel for about 5 months. 200k mi. Daily work driver and tow vehicle. Is any other Duramax owner experiencing this? Have you technicians run across this at dealership?
The question is: Does anyone know why mpg calculation by hand is 4-5 mpg lower than what DIC is showing? This is not about my mpg, but why is the computer showing much less fuel used than actual. My other trucks and Tahoes were usually only about 6 tenths off, not 5 mpg. A consistent example would be a fill up of 20.9 gal, while the DIC shows 14.38 gal used. (11 mpg vs 16 mpg). Over 6 gal difference. DIC reset with each fill up.
Where does the computer measure the amount of fuel used? Pump revolutions or a flow meter somewhere? Is it dumping excess fuel because it thinks it is "leaning out" under power?
This has been consistent in town towing or on the road. Every fill up. I try to park level when fueling & fill to the same spot in the tank hose.
It has needed injectors and they were just replaced. Same results, but mileage was better.
So technicians, do you know the answer or can you look it up in GM's problem solving database?
Thanks for your help.
2500HD 4 x 4, Crew, MBRP exhaust, cat delete, Bully Dog CAI, Edge tuner w/ Attitude, 265/75-16 BFG T/A's
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