[MetroMPG]

Interesting question. Usually it's the guys with pre-OBD-II vehicles that are looking for more accurate ways to measure fuel used at the tank.

I don't know anything about fiddling with OBD-II. I'd be surprised if you could feed a new sensor into the system and then have the gauge read it though.

But I think you'd be able to buy or make a higher resolution digital gauge easily enough. You'd just have to calibrate it against an actual fill (done in measured increments) for accuracy.