dash mpg display

the dash is using the information in the computer, tire size, gear ratio, eyc... Get your mechanic to correct the information in the computer, it will still be off a little due to tire wear.

 

I don't think you can. Mines fairly accurate within a gallon, I always reset after filling up the tanks. That might help

 

mines 10% off. I always just subtact 10% and its dead on. Excessive APU use (over wee-end) will throw it off to.

 

not sure about detroit engines, but volvo and MBE may be calibrated. Really dashboard display just reads data saved in engine ECM memory.

 

The in dash displays dont now how much fuel is used. Fuel use is hard to figure out. The fuel going in isnt bad, but the return line varies considerably. The computer uses o2 sensors and a series of calculations to guess at the fuel usage. Truth is, the calculations arnt 100% right. Every motor is differnt and the calcs are one size fits all. lmost every truck does not accuratly display mpg. IF you get a scan gaudge, some allow you to out in a % correction to mae it more accurate. My s60 detroit is set at -17% fuel ussage and it is dead on. My cummins is set at +10% fuel ussage and is close. That truck has an apu that the engine computer doesn't take into account.

 

How about one of those scan gauges I hear being sold on the trucker radio? Are they any good and accurate?

 

the KR scan gaudge allows you to calibrate it. you can add or subtract a % from the fuel used so it is pretty accurate. Mine is normaly within a 1/10th of reality.