What is the best was to track the fuel you burn on site? I have seen companies run the odometer while pumping to track the mileage. Is there any other way such as adding a second odometer?  

Seed, If you have an hour meter, use that. You will have to get info on how much fuel the truck uses at X RPM's and under what % load, but that would be the most accurate. Might be better to Time how long it takes you to run through a tank, including driving, pumping, and any other run time then work it like you would fuel mileage. For Ex. You have 80 gals of fuel, and it takes ya 4 days to run through it, you are using 20 gals a day, 2.5 gals/hr. Then you can better figure out how much a day or even hour your fuel costs are.

If you have an E-Mack the computer knows your fuel usage while in PTO.

bob I have a '99 mack on a telebelt It is a rd model do you think my truck has that? if so do I need a dealer or a computer hook-up to find the fuel useage with pto's engaged? I should be able to claim that as non-taxable fuel! thanks terry

My best advice is to talk with your Mack dealer. He knows. I would ask for the service manager, he will help you and give you the best/current information. ;~)

get a hubometer,set your trip meter every day,subtract the daily hubometer reading from daily trip meter reading