Should I delete some gaslogs
 

I have some gaslogs that may or may not be to accurate. For example I had a fill of 33.8mpg only going 30 miles and another one that is 15.06mpg going 55 miles. Should I delete some of these entries or just let it be? I'm starting to only fill up when I'm about a quarter of a tank now.

As long as all of your fills/mileage have been recorded it will average out just fine.

Yeah, just leave it to average out.

well.. they still count towards your cars mpg right? i mean your average would not be accurate if you didnt log a tank of gas.

in my garage, every single tank has been logged so the numbers for the fit account for every drop of gasoline consumed and every foot traveled for the life of the car. and the same is true about the amount of time that i have owned my civic.

Dpnt throw good or bad tanks away. read last paragraph
 

Those 'errors' are prob because you did not refill to the exact same point as the previous fillup. Usually this can result in an error of no more than 1mpg on a fillup, but the error can 'seem' to have exagerated results when only going a few miles. For example being off by half gallon (let assume 50mpg) on a 2 gallon fillup will yeild following results:

Normal, no error: 100 miles using 2.0 gal = 50 mpg
Under by 1/2 gal: 100 miles using 1.5 gal = 66.7 mpg
Over by 1/2 gal: 100 miles using 2.5 gal= 40 mpg

Now with a full tank the errors are not so obvious. Look at a 10 gal fillup:
Normal, no error: 500 miles using 10.0 gal = 50 mpg
Under by 1/2 gal: 500 miles using 09.5 gal = 52.6 mpg
Over by 1/2 gal: 500 miles using 10.5 gal= 47.6 mpg

This is why its important to try to do full tanks. You get a better idea of what you car is doing. There is too much room for error with a small fill as even the slightest variances can yeild wierd numbers.

The irony is that you actually NEED those tanks to remain consistent and have accurate overall readings. Your next tank may not be as sweet because of that 'high mileage' tank. Everything will average itself out. If you throw out that high tank then your overall mileage will UNJUSTLY suffer. Anyone can 'cheat' a good FE tank by OVERfilling a tank and choosing not to overfill to same level. However that OVERFILL caused the previous tank to have lower FE numbers. My point is that it will always average out. So never throw out a tank unless there is definitely an issue that causes reading errors (as oppossed to natural varances and fluctuations). Such a case would be if someone added gas to your tank and did not record the gallons.

popimp -

I would leave them in. Maybe modify the comment where appropriate. The 90 day average will be what people see. I think the whole gaslog is important for "looking back" and understanding the car's performance gains/losses over time.

CarloSW2