How to calculate MPG / fuel economy formula

[jomelmaldonado]

Hello everyone, in Puerto Rico, where I live, fuel is sold by liters, instead of gallons, so I have to divide total liters purchased by 3.7854 to convert to gallons. I've been using an Excel spread sheet I prepared about 5 years ago and have been modifying since then. I have used this spread sheet for my Suzuki Swift, Jeep Cherokee and Ford F-650 Tow Truck. I am going to include the link for any of you that might be interested in it.

You simply enter the following data:
Odometer reading, liters purchased, date, Price/Liter and Fill Up Cost

Optionally: Location, Fuel Station and Remarks/Notes:

It will then calculate the followings:

Miles Driven
Galons
MPG
Average MPG
Price/Galon
Fuel Cost
Total Fuel Cost
Total Miles
Miles used so far
Miles Loged
Gallones Consumed
Cost per Miles
Overall MPG
Fuel Cost

It also has to graphs, a MPG graph and a Cost graph


Plus it has a part where it reminds you on the next tune up items like for example:
Oil & Filter
Air Filter
Spark Plugs
Ignition Cables
Coolant Level
Coolant
Brake Fluid Level
Front Brakes Check
Rear Brakes Check
Front Brakes Pads
Rear Brakes Shoes
Tire Pressure
Timing Belt Replace
Ribbed Belt Replace
M/T Fluid Level

This spread sheet is pre-filled with some information of my Suzuki Swift, remember to change it accordingly could be modified and tailored at you're convenience: Any question, feel free to ask, help this spread sheet is useful those that are starting at this, or want to keep a better, more precise and organized fuel log.

[oldblue]

Tire size calculator Tire size calculator Axle ratio calculator Axle Ratio calculator

[cighon]

have a hardback field book in my glove box, keep all details on my truck, gas, oil change, etc in it.

[rbrowning]

I too kept a hard cover book in my console for each vehicle for years.

It was amazing to see the step up in MPG in May and back down in Sept./Oct every year. I asked a "carburetor engineer" that worked for Chrysler and he told me about the different formulations for winter and summer gas.

It also showed that one tank meant nothing but more than a few were harder to do under similar conditions. For 6 months I was burning about 10 gal / day and it gave me a good chance to compare a couple brands A-B-A-B etc for 10 tanks of each and found that the Silverado got 1.1 MPG better on Amoco than Speedway (YMMV).

I also noted that even with Mobil 1 and all highway driving that my mileage would begin to degrade after about 8500 miles even though the oil still looked clean and felt slick.

After I got my Impala I found that the computer's record per tank was within .7 MPG of calculated so I go lazy and quit keeping the paper record.

[Old Tele man]

...been keeping log books in my cars since 1965...in every car since.

...section I = FUEL: mpg fillups
...section II = FLUIDS: oil changes; transmission fluids; coolant change, etc.
...section III = ELECTRICS: spark plugs, battery/alternator, lamps, fuses, etc.
...section IV = SERVICES: recalls, engine or transmission repairs, etc.
...section V = PARTS: what's "equivalent?" ie: GM partnumbers vs. aftermarket parts.

[phw]

To view links or images in signatures your post count must be 10 or greater. You currently have 9 posts What does this mean??????

[phw]

Nice work. Thank you

phw

[Mifunego]

Originally Posted by MetroMPG

Good points. For "moderate" fuel economy types.

You will know you've gone hardcore when you proceed to step 8: validating your odometer's accuracy and adding a correction factor in all your MPG calculations because it drives you nuts that it was off by 1.5%

I don't know if this is "hardcore," but as there are mechanical discrepancies, as well as tire size discrepancies, and it seems many of us change tire size too (you can't really believe the size on the tire is perfectly accurate - it varies) you might want to check the accuracy of your odometer reading this easy way: Pre GPS days (2004 for me) I would sync the odo (or trip odo) with the milemarkers on the expressway when I had a long trip. Much easier to do these days with GPS. Use that adjustment when calculating mpg.

The odo on my car, with the winter tires, is 100.95% accurate. Or I'm accumulating about one extra mile on the odo per 100 driven. Pretty close, but when you want to see that exact mpg...

[debbott]

This thread is very interesting. I am going to start keeping track of the fuel efficiency in my truck. There are variables to this due to transporting big canvas projects (increased weight/resistance) on some of my trips. Will post some of the stats when compiled. Debbott

[02ws6]

I keep track of my fuel mileage and I like to make sure I get pretty close but some of you guys astound me at the attention to detail you give everything...

I guess in order to have that perfect combination, you need attention to detail.