Which of my 3 readings is wrong? milage, engine hours, fuel usage?
 

Hi,I bought a new 08 suburban with about 10 miles on it, we have had it for a year and a half.now the odometer reads 39990, the engine hours reads 402, the fuel usage reads 827 gallons, it averages 15.9 mpg..none of these measurments add up to 39990 miles..any ideas thanks!

Gallons used and average MPG are resetable (I reset them both every time I fill up) so don't expect them to calculate to your current mileage.

Didnt know that, thanks for the info..what about engine hours?

I don't know about engine hours, I haven't tried that one, I figured it wouldn't be of much use if it was. If you want to try just press and hold down the check mark when the option you want is displayed.

Also even if you've never manually reset the other stats if the battery was disconnected for service that would clear them out as well.

Engine hours are cumulative and are not resettable,EXCEPT when the dealership fools with the computer. I've had 2 BCM re-flashes done, and each time my engine hours are reset to "0". I think if the hours are written down before the reflash, they can be entered into the computer, and it'll pick up where it left off. So basically, engine hour readout doesn't mean squat because you can't trust what you see. At one time, I thought it waould be fun to open a thread on the forum and compare mileage to engine hours. It would have given you a lifetime average MPH ( I think I would have claimed that prize), but after the reset happened on my computer, that idea went out the window......

My engine hours on my 07 reset once while jumping it off when I had left my lights on.

Remember that engine hours add up when idleing as well. I think the engine hours just help the oil life indicator calculate between miles & hours to let you know when to change your oil. There is alot more involved in the oil life indicator as well, driving habits etc..