Originally Posted by nomenclator

To calculate your fuel efficiency is very simple. Fill up your gas tank, write down your odometer reading, Call that Reading One, or R1. Then after you drive around for a while, till the tank up a second time and write down your odometer reading again, at that time. Call that R2. Also write down how many units of fuel it it took to fill the tank..Call that Fuel, or F. Fuel efficiency, in distance traveled per unit of fuel, which we will call E equals the difference beteen R2 and R1, divided by F. Or in the more concise language called algebra, (R2 - R1) / F.

If R is in miles and F in gallons, then E will be in miles per gallon. If kilometers and liters, then E will be in kilometers per liter. To get gallons per mile or liters per kilometer, divide 1 by E.

I took a look at fuelly.com to see what they say about how to calculate fuel efficiency, and their explanation not only didn't match mine, but it didn't make any sense. In one video they say write down your odometer reading on your receipt when you "fuel-up." Well, it's not enough to "fuel up" your vehicle. You have to fill your tank, not merely fuel up. Then they say when you get home enter "these values" at the fuelly.com web site. For fuelly to calculate fuel efficiency you must enter the amount of fuel it took to fill you tank. But they say nothing about entering the amount of fuel it took to fill your tank. They just say "these values." That instruction is too vague to be of any use to anyone. If I did not know how to calculate fuel efficiency, I would not be able to learn how, from their web site. I would have left it totally confused.

Originally Posted by SilverEX15

I see what you mean, but I don't think either will run indefinitely. I'll check that.

Originally Posted by Brian Jones

I have a 2015 with 95K miles. It had been getting about 40 mpg average (42-38, occasionally 45). Just a month ago, the fuel economy started going down. Now it is averaging 36 mpg. Same driving situation, except for temperature. I live on the Oregon coast, so the temps. have dropped from an average of 60 degrees to an average of 48 degrees. I know, not much of a change. That's coastal living for you.
When I saw the slide happening, I changed the plugs since the old ones had 95K miles on them. I used the exact same NGK plug as the original and checked the gap carefully. Then I inspected the air filter, which I had replaced about 3 months ago. It looked very clean. I checked the tire air pressure. One tire was 2 lbs low. Topped it up. All the airflow parts are in place and tight on the bottom. I plan to try the Techron as others have suggested to see if that makes any difference. If it doesn't, I'll assume the change is due to the change of season. The car has run beautifully for nearly 100k miles with one exception. The variable valve timing control (VTC) has increasingly caused a pronounced rattle when the car is started after sitting for awhile. It's so bad now that I couldn't sell the car if I wanted to (I don't). It started the rattle at about 8K miles and has gotten progressively worse, especially in the last six months. But I don't see how this particular problem (shared by other Fit owners) could affect the fuel economy.

Originally Posted by Jazu

I've improved my mpg mesurement variation by filling the tank (pump kicks off) then add exactly 1.0 more US gallon of gas to my 2019 Fit LX (it was 1.7 gal on my 2002 CR-V and 1.4 gallons on my 1992 Integra GS-R). What this does is ensures the tank is filled to a more consistent full volume across fills.

Originally Posted by 2Rismo2

Pump 1 fills up and stops 7.7 gallons. You add one more gallon and you're now at 8.7 gallons

Same scenario, but pump 2 fills up and stops at 7.9 gallons. You add 1 gallon and now you're at 8.9 gallons.

I don't understand how that makes the fill-up any more consistent. Please explain to me like I'm a caveman.

Originally Posted by SilverEX15

The best way to fill the tank consistently is to fill it to the point where it is about to spill out onto the ground. Then you can get a really accurate computation.

Of course, if you just keep track of how many gallons go in and how far the car goes, you can divide one by the other and get an accurate figure.

Originally Posted by SilverEX15

The best way to fill the tank consistently is to fill it to the point where it is about to spill out onto the ground. Then you can get a really accurate computation.

Originally Posted by George Knighton

Update for my “best ever” is 51.2 miles per US gallon.

Slightly more than 60 miles traveled and circumstances allowed ACC to maintain 60 mph, which is apparently the best compromise rev for a CVT.

Originally Posted by 2Rismo2

Not trying to be argumentative, but what's the use of keeping track of the best trip MPG? I track my MPG by the tank and that's good enough for me.

Originally Posted by 2Rismo2

Not trying to be argumentative, but what's the use of keeping track of the best trip MPG? I track my MPG by the tank and that's good enough for me.

Originally Posted by 2Rismo2

Fair enough. I track the tank MPG as it's a good indicator if something is going on with the car. If all of a sudden there is a huge MPG drop, then something is not right..

Originally Posted by SilverEX15

Yes, that is a good reason to keep track of mileage, but the Fit does that automatically, and we will see at a glance if there is a sudden drop.

Originally Posted by George Knighton

There is no point.

It is just interesting how high an MPG the GK5 can produce in the right circumstances.

Of course, even a short period in stop and go will cause it to plummet.

Originally Posted by Jazu

I track my MPG for maintenance reasons. It all started on my 1992 Integra GS-R...

Originally Posted by exl500

I live a simple life.