My truck's fuel consumption calculator is completely off, it's like 1mpg less vs manual calculation.
How exactly does truck's computer calculate mpg, so I can start figuring out what's wrong?
The engine is pre egr 12.7 Detroit in a Volvo 770
Fuel consumption calculation
Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by DUNE-T, Jan 7, 2021.
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Wouldn't think there's much you could do to make it more accurate unless your speedometer is off but then your calculation would be off to. -
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Don’t worry about the computer being off . It doesn’t actually measure the fuel flow. It is just an estimate. Some trucks are close, many can be out 20% or more.
Pen and paper is the only accurate calculation.AModelCat, Goodysnap, magoo68 and 1 other person Thank this. -
I have a brand new 2021 that's off all the time. If you idle much, or do a lot of city trucking it gets even worse. The only way to really measure is to hand calculate it when you fill up.
Just slapping a new bigger turbo on the engine is not going to necessarily increase mileage. There has to be tuning to go with it in the ECM. If that wasn't done correctly, the inputs the fuel mileage readout uses to display the mileage may be off by quite a bit.BoxCarKidd and lester Thank this. -
Something is off and I am not sure what yet.
I always do hand calculation and my other the same model trucks are usually close to what computer shows, but this one is just way off and that bothers me. -
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When I purposely leave it idling, the computer shows 0.2 gal/hr, while my other trucks show 0.7-0.8.
Something is definitely not right with this truck's computerLast edited: Jan 24, 2021
Dave_in_AZ Thanks this. -
My 99 Classic had the Detroit dash computer on it. It always read higher than actual. I heard it was based on RPM readings. Don’t really know how it works. I used it to refine driving habits. What I noticed is the higher the computer went, the more it lied. 7.5 was actually 7. 8.5 was 7.75, 10 was 9. I hauled very light loads, and got amazing fuel economy. It was a pre Lo Nox engine. It was interesting for a while. But got tiresome. Finally just started running it how I wanted to. Mileage settled in at around 6-6.5 for the life of the Truck.
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