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

[hat_man]

Hello everyone.

I was reading threads in the Success Stories area to see what good ideas I could glean from other's success. My old truck, Little Black Ranger, (R.I.P.) is now gone and I have a new Ranger called Oh Deer. Same aero be damned shape (before I start modding ) but a newer engine. 2.3l Duratech in the new truck. I don't know too much about them yet but I'm learning. I know the new truck is capable of more so I compare posted FE numbers to mine on a "curve" so to speak.

As I'm reading I see great FE numbers posted (higher than mine) but usually on short runs. Then I see good numbers posted (slightly higher than my current numbers) but over a full tank. My question is.....is there a preferred method to post FE numbers? If I posted in a thread my FE on the way to work only my truck would look great. It's more downhill than uphill and if there is any wind at all it's usually a tail wind. Of course on the way home it's the opposite and the numbers wouldn't be nearly as good. If I post for the full tank it's an average of the two and probably closer to a "real world" number.

Now don't get me wrong. I'm not saying either is right or wrong. I just wonder how you all choose. I can see the benefits of both ways.

Thanks.

[Big Dave]

My two cents.

I go bottom line. Gallons put into vehicle at the pump vs miles on the odometer.

Also I average out over at least four fill-ups to average out day-to-day variations.

[Ecky]

For my fuel log, I use odometer-reported miles traveled (to the nearest tenth) and gallons reported by the pump. I have to trust the pumps, there's no way around that. To ensure that my tank isn't being filled to different levels, I don't miss reporting any fillups - that way if one tank is a little short, the extra will be a little tall, and they'll average out.

The fuel economy gauge in my car usually disagrees with these numbers by less than 2% on whole tanks, so I have a lot of confidence when using it for shorter trips. I take trips that are less than 10 miles with salt, and throw away those where there's obvious significant elevation change. It's not so much that I doubt them, but that there were environmental factors that cause them to be artificially high or low, which will average out over a tank.

101mpg over 104 miles on level ground, tank isn't yet showing less than full :

[cowmeat]

I'm too lazy to keep up with the daily EV fuel log for the Volt, but when I had my Insights I would top off the tank at the same pump at the same gas station at the same time of morning, recording the miles driven since last fill up and the amount of fuel added at the fill up.
Since the Insight would go about 700 miles on a tank, that's about as accurate of a number as you can get in a car. When you drive 712.6 miles and divide that by 9.52 gallons, it's pretty accurate and simple math to get an overall mpg average

[Daschicken]

I fill up at the same pump each time whenever possible. If it’s busy, I wait. I use the same fill up technique too: Full speed until the last 2-3 gallons, then slowest speed. Let it auto stop and pull it out, no topping off.

My highway commute thankfully doesn’t have your elevation dilemma, numbers are repeatable in both directions. For record trips I use the scangauge, as long as it’s within 1% at fillup time I don’t adjust its numbers for record trips. To get more accurate I would really need a gauge that reads actual fuel injection pulses. For your differing elevation trips I would just suggest averaging the two as your trip mpg.

I also have slightly larger tires than OEM, so I use a multiplication factor for miles when calculating tank mpg.

[redpoint5]

Generally I run the tanks well into the gas light turning on and fill to full, recording the miles according to the odometer and the gallons used to fill.

I've got a truck with a bad odometer, so I have tracked distance with GPS, and record gallons using a cheapo fuel meter attached to my diesel pump.

Sometimes I might fill up early, but all that gets averaged out in the long run assuming I record every fill up.

[ksa8907]

I have a Chevy volt which is difficult to separate EV and gas miles. I only calculate mpg in the garage here. I use the display everyday and make an entry based on gas miles traveled vs gallons consumed.

I have issue with those that cherry pick their numbers or who exclude tanks for various reasons. I don't exclude anything, I want my data to be a true representation of what anyone should expect to get with the same vehicle.

[hat_man]

I wasn't thinking anyone was really cherry-picking. I was just reading things like "Record FE of xxx on way to work." or similar posts. Unless the commute to work was close to 100 miles it would seem to skew the numbers. I preferred the miles on the odometer divided by the gallons at the pump method until the filler neck on the old truck started leaking. New truck = non leaky filler neck. Can't wait to start modding and see what this truck can really do.

[Gasoline Fumes]

One-way FE numbers are really only useful when compared to different days or different vehicles on the same route. If you get 35 MPG going to work, try for 36 the next day! Round trip FE is more useful for comparing to other people's numbers.

I have no FE instrumentation and can only calculate by tank.

[Stubby79]

Fill tank. Reset Odometer. Divide one by the other. Anything else doesn't really represent "real life" and/or what my wallet sees.