How do YOU calculate the FE numbers you post and why?

[jcp123]

Looks like I'm not the only one, I just use the trip meter and divide by the gallons at the pump. It's not perfectly scientific or accurate, I'm sure, but it is at least consistent.

[California98Civic]

OEM odo miles displayed and gallons shown on fuel pump. I modify that with a GPS derived multiplier because my non-standard wheels, or OEM design on the car seems to create a miscount of the miles. If you calibrate your odo like that, use several longer trips (100+ miles) to reduce data noise. That's what I did.

[19bonestock88]

I just zero the trip at each fill up and divide it by the gallons used to fill the car... I go to the first click...

I also use a multiplication factor when I run taller than stock tires, rounding down to the nearest whole percent... at the moment I’m adding 3% to the trip meter display when I fill...

[hayden55]

Yup for sure I turn to something like Fuelly or the Garage here. Too many times have gauges been wrong, besides the odometer and typically the gas pump is correct.

[redpoint5]

One nice thing about my Prius is that it has an average MPG gauge built in, and a 10 gallon tank. This means calculating the range is so easy, a caveman can do it. Simply take the average MPG as displayed, and tack a zero on. That is close to how many miles I can expect to get on that tank of fuel. At 50 MPG, I can go 500 miles on a tank. (The rated capacity is 10.4, so that leaves a small buffer). The fuel light always turns on when I have over 100 miles of range left. I'm very comfortable going another 60 miles while the fuel light is illuminated. (I've run completely out twice, but I have EV range as a backup).

[slowmover]

Just use Fuelly or a journal. All gallons and all miles. Engine hours, also.

MPG shouldn’t be an isolated number. Not useful by itself. Needs to be paired with average miles per hour.

The pair need to be seen over about 3-5000 miles for an accurate snapshot. Tank by tank is worthless.

A full calendar year to account for weather and other changes.

Bring to annual cost per mile. Dollars spent and gallons received. Expressed as cents-per-mile.

At $3/gl my annual cost is .08/CPM. Been this for years. The variance is fuel price. I only need estimate miles driven.

If you want to cut fuel budget it’s as much about miles driven as vehicle spec.

Stunt driving might be fun, but it’s a dead end.

How one fills tank, etc, is beside the point. Cut the miles to achieve same end. Exert discipline about idling.

The rest just doesn’t matter.

[me and my metro]

I kept detailed records for years when running my Metro. Now with this Saturn L200/5 I have verified the accuracy of the odometer by gps. This car has a trip meter and I refuel at the same pump at the same station. This car gets 29 mpg consistently tank after tank. This is just under the EPA highway rating of 30, but much better than the 22 city rating. I have a 30 mile commute part highway at 60 mph and part city stop and go.

[19bonestock88]

29 average isn’t bad considering your 4.4x final drive, and that it’s a midsize car... you verified the odo with GPS?

[jcp123]

Originally Posted by 19bonestock88

you verified the odo with GPS?

That's why I said (above) that I don't think my logs are terribly scientific. That and pump error, which I mitigate other ways but could not possibly eliminate. Comes down to what kind of effort you want to make.