Scan gauge vs actual. Help.
 

Okay so I just filled up tonight.
Car now has only 610mi on it and I just went 310mi on 7.2 gallons.
43mpg exactly.
My driving is nearly 100% suburban city stop and go. When I go on the "freeway" it's for 5mi tops. Mostly I just stay on the side streets though.

I'm pretty happy with that. Tires were at 36psi. And most of that tank the temps were still cold, 30s mostly.

My scan gauge guessed 6.8gal so I had to adjust it to 7.2. Hopefully it keeps getting more accurate as I go.

Do you guys think it will slowly get closer and closer to the hand calc. Number?

In my Explorer I kept a spreadsheet that kept track of the discrepancies between the scanguage and my fill-up calculations. Combined with a speed adjust I ended up ~ -4% on the calibration, but I was still sometimes up to 5% off. It was generally accurate for most of my driving, but would under-report my fuel use a bit when I got a lot of DFCO cycles. It sometimes stayed on 0.0 LPK for most of a second after I would start accelerating again.

I didn't seem to have the same problem when using the same scan guage in my Versa.

When setting up my gauge I would go half the difference. Remember you can have fill deviations. You could also use several tanks and average them.

Dfco is when the injectors cut fuel right? I try to coast as much as I can and it goes to 9999. I guess there is a setting if I want to set it so it doesn't go to 9999??

Oh that could be too. I will see what it says next fill. It gets such good mileage it will take awhile especially having another vehicle and a scooter I switch off with haha

OBD gauges measure air, not fuel, so they can only ever be 'somewhat' accurate.

My advice is to settle on a calibration and leave it. The outright accuracy isn't really that important in the overall scheme of things. Set it to be a little on the pessimistic side so it encourages you to work a bit harder.

If you want improved accuracy and don't mind hard wiring, look into a UTComp. It measures fuel, not air.