How do I know how much fuel I am really using?

50 gallons short?? Is someone stealing your fuel while you are parked? Also I would never trust a dashboard fuel gauge in a heavy truck. I would keep track of miles run and gallons to fill to capacity and keep a running tally every day. Forget the electronic fuel monitor, qualcomm etc. Know your trucks fuel capacity, start with full tanks and figure usage every day.

 

The only 100% accurate way to track fuel usage is to log every fuel purchase and divide miles per gallon. I do mine at the end of the month so I get a total for the month. I don't rely on what my elog says as its just an estimate based on computations from the ECM and its own internal processor. If you consistently are getting ridiculous numbers for fuel mileage when you do your own math, you need to think of what could be causing the problem. Is there a mechanical problem with the truck? Is there a fuel leak? Or could somebody be siphoning from your tanks when you park?

 

Those fuel monitors use some sort of computer program. The qualcom usually goes off what is programmed into it for what the company thinks you should be getting. Neither one, even if they happen to match, are very accurate. You need to manually calculate it yourself each time you top off your tanks. Divide the miles driven since the last top off by the number of gallons you put in. Do that for awhile till you get an idea what your truck really gets for fuel mileage. Its the only way to really know, as fuel gauges are not really too accurate either.

 

Would one of you care to expand on the mpg calculation method?

I get what you all are saying, but say you put in 100 gallons and you go 350 miles then you get another assignment and put another 75 gallons in wouldn't your calculation be off because you wouldn't have an accurate measure of how many gallons are left out of the original 100 after the first trip?

 

You start with full tanks. The next time you take on fuel you have to again fill the tanks. If you do not fill to capacity every time you have no way of accurately calculating fuel mileage etc.

 

Just keep up with how much you put in each time you fuel without topping off and add it to the gallons the next time you top off. Total your gallons together and use mileage from last top off. This is how I do it between fills.

 

Ah yes I've got it now. Thanks for the explanation. I appreciate it.

 

Here is a simple iPhone app that I use every time I refuel to calculate and save my mileage. You only type in miles and total gallons and it does the figuring for you. Very simple, no frills, app. The name of it is Mileage Keeper.



An actual screen shot from my mileage. It shows mileage from each fueling and keeps a total average mileage from all fuel.