You can claim that, but I would claim you are wrong. I have been keeping gas mileage records for almost 20 years. I drive the same trips over and over. I have alwys found significant difference for single fill-up fuel mileage estimates. However, if I average over multiple fill-ups, the estimates smooth out. Over the years I have tried averaging over 3, 5, and 7 fill-ups. I find a averaging over 3 tankfuls is good enough (5 is better, 7 is better still, but no that much better).
I am not claiming that the gas pumps are inaccurate. I am claiming that you don't always fill the car up as full. Small differences in car position, pump kick-off, etc can make significant differences in how much gas you get in your tank. Here is some data I have collected:
Moving Average MPG over # Fill-ups Fill-up 1 3 5 7 1 14.7 14.8 15.0 15.0 2 14.8 15.1 15.3 15.1 3 15.5 15.7 15.2 15.1 4 25.3 15.5 15.2 15.0 5 14.6 15.1 15.2 15.1 6 14.8 14.6 15.1 15.2 7 14.2 14.9 14.9 15.2
This data is from February of 2003, for a 2003 Expedition that is mostly driven on the same repebreastive 300 mile round trip. Now if I wanted to be funny, I could claim that my Expedition gets 25 mpg - which it doesn't. But for that one fill-up, I got a really wacky averge (only purchased a few gallons for that stop, so the fill-up error was magnified). However, over 5 tankfuls, the average was smoothed out to my typical average. I use moving averages. For example, the 7 thankful average is based on the center fill-up, plus the three before and the three after.
Ed
