Originally Posted by sryken89
05Train...your message makes sense, but no matter whether its the last 20 gallons of my truck ran to empty, or the first 20 gallons from the top of the tank, 20 gallons is 20 gallons....so unless there is something huge hiding that I am missing it seems pretty common math to do. I will see on my next fill up what hand calc comes to.
How do you know how much gas is in your tank when you start filling it? How do you know when you've used exactly 20 gallons? It is very simple math to do if you can answer those two questions, and the only way to know that is to run the tank dry. You can't count on the "full" tank being exactly 26 (or 32) gallons either, because the pump shutoff is going to occur at different points as well.
So if you fill the tank until the pump shuts off, drive it around, then refill it until the pump shuts off, you'll be able to hand calculate it relatively closely, but you're doing that based on the assumption that the tank was equally full to begin with. That can be a really inaccurate assumption.
The EVIC bases its computations on consumption, and you've got the odometer and DTE displays to work with too. That's going to be more accurate.