I was wondering how this is calculated. I mean, every time I fill up, I fill my tank full
all the way, but yet I don't let my tank get completely empty before I fill it again. I usually wait till it gets to around quarter of a tank left before I get gas. Will that throw off the numbers? Or does the tank have to be on empty for an accurate reading?
The amount of fuel purchase makes no difference as long as you always fill the tank. The only time variances really make a difference in the short term is if you do a "short fill". This is when you top off the tank when it is already 3/4 full or more. Any variances from tank to tank will even out in your overall average, but for greatest accuracy I recommend always going ot the same station, and pulling up to the same pump, facing the same direction. Set the pump at the maximum fill rate, and when it clicks off, do not top off the tank... Just hang up the nozzle, you're done.