I always measure mileage like this: - Fill to max. - Set Trip B to zero. - When it's time to fill up again, fill up to max, see how many miles are on Trip B compared to how many gallons I had to fill up to get to max. I've done this countless times on all kinds of vehicles and the car's computer is always a few MPGs (2-3) better than what it is in actuality. Why is this? If it's just an estimate, I get that, but how come it's always in the favour of showing better mileage than you're actually getting? I also wonder when people list their MPG figures, if they're actually calculating by hand, or if they just rely on the computer. PS. I never pump after the first click, so it's not like I'm filling up the hose.