Mine still says 20 but I only have 600 miles on it, so hopefully it gets better........

While I agree with you completely this method is going under the assumption that the gas pump is putting the correct amount of fuel in your car as what it says.

Gas pumps are supposed to be regulated and calibrated but last year local news in my area did a big feature on this and found that many gas pumps do not put in the actual amount of gas they are displaying. It was discovered that about 75% of the gas pumps in my area were giving you less gas than displayed. Average was about .5 gallons less per 20 gallons but there was a gas station or two that gave a full gallon less per 20 gallons. Another big find in the feature was that the gas station itself (brand or reputation) did not matter. Big brands and well known gas stations were just as likely to rip you off as little ones.

Yikes. I actually think one of the Shell stations near me is not providing the correct octane as advertised. My mpg has actually went up since switching over to a Chevron station near me.

One station near me is giving alot more than what the pump is displaying... gonna enjoy it while it lasts. ;)

My readout is indicating a 28.5 mpg average (prob 27 real-world). Not bad for a car that mostly sees stop/go driving, is redlined daily, and gets autocrossed. Very happy with the mileage. With more highway driving, I bet it'd be even higher.

The digital read out has been incorrect every single fill up I've ever had in my FR-S. It usually reads high by 1-2 mpg. That being said, my best mpg on a recent highway trip was 32.6 MPG. I've averaged 28.1 MPG in the 5200 or so miles I've put on it.

I'm flying out in June to get my BRZ and then drive her 1400 miles home. I'm gonna see what kind of MPG's she puts down.