Blog Post

AccuFuel: Calculate and Graph Your MPG

I used to always fill up my car completely so I could do a quick MPG check against my trip meter, but with the price of gas lately I’ve been reluctant to spend $60 or $70 at the pump. I needed a tracking log so I could figure out my MPG across several partial fill ups. Some of you may also be interested in maximizing fuel efficiency or even hypermiling. AccuFuel (formerly named MPG) stands out among the various mileage tracking choices in the iTunes App Store. “Polished” is a word that gets used frequently in iPhone app reviews (at least for the good apps) but it certainly applies to AccuFuel.

Using the app is simple. You click on the “+” button on the gas pump on the main screen each time you fill up. Then you enter in the odometer reading, gallons, and price per gallon. You can also specify if this is a full or partial fill up so AccuFuel won’t get confused if you only decide to drop five bucks in the tank and top off the tank later in the week. After at least two complete fill ups, AccuFuel will calculate your fuel efficiency and present a graph along the bottom of the home screen.

AccuFuel can track your fuel usage for multiple vehicles. When adding a new car, AccuFuel will let you select from a list of vehicles to automatically display the expected fuel efficiency, but only from 1998 and newer. For older cars, you can enter the details manually so you have a baseline against which to compare your actual mpg.

You can export your entries as comma separated values in an email message and send them to yourself for backup or use in another application like Excel or Numbers. One cool feature is that these email messages contain a link that will push the .csv entries directly into AccuFuel.

One thing I’d like to see in the next version is a graph of gas purchase prices over time. That data is already in AccuFuel along with the fuel efficiency data and it seems like it would be easy to tap to toggle between different graphs for MPG and $/gallon.

I tried several fuel efficiency apps, and AccuFuel definitely stands out as the easiest and best looking app. There are apps that include fuel efficiency along with other features, but AccuFuel is the best for a straight efficiency tracking app.

AccuFuel is available in the iTunes App Store for $0.99.

15 Responses to “AccuFuel: Calculate and Graph Your MPG”

  1. flexan

    So, to be clear, if I put in $5 one day, $10 another time, $14 another time, and say $5 again another time but EVERY time I fill the tank to the top, then I would use FULL every time and never use partial?

    i.e. I always filled the tank completely, but I just stopped at the gas station with different amounts of gas in the tank on those various trips.

  2. @Weldon: There it is! That makes good sense to me, and also explains why I would never use the ‘partial’ option on a routine basis; I’m one to fill the tank back to full. So, the partial option is for those that put in $10 here, $30 there…

    phew. I can’t believe it took me so long to get this.

  3. @Tim – you use the partial fill option anytime you don’t completely fill up the tank. That way if you use drive 200 miles and use 10 gallons of gas, but only put 5 back in at the pump, AccuFuel won’t assume that you only used 5 gallons to drive 200 miles.

    If you always fill up the tank completely then you would never use the partial fill option.

  4. @Tim – I’m not sure, I don’t know how to use the s/w. I don’t know what the application does with that information. In general, the “partial fill” issue can dramatically effect the gas mileage for your most recent trip. As you gather data points over time, the running average will be less effected by a partial fill.

    If you average your gas mileage over time, it’s similar to dividing all the miles driven by all the gasoline consumed. If the numbers are large (10’s of thousands of miles and thousands of gallons of gas), the few missing gallons don’t matter than much.

  5. @jgohlke it’s starting to make sense! So what you’re saying is that if I always fill my tank when it gets to half-empty, I should be using the ‘partial’ fill option?

  6. @Tim – You actually need fuel “consumed”, not input. You don’t care how much gas you get or how much is in the tank, you need to know how much you have used. The gas you are putting in now is for future use and will be used to calculate your fuel mileage for the next trip.

    To calculate the fuel mileage for your previous trip, you need to know the miles driven and the gasoline consumed.

    Using the amount of fuel you input is just an easy way to measure the fuel consumed. There are many ways to determine this, filling to the top is just the easiest way.

  7. @jgohlke

    Thanks for the explanation, but it still doesn’t jive with me. I can see your reasoning, if you weren’t asked every time for the odometer reading on the car anyway. As you say, you need both fuel *input* and distance traveled to calculate mileage. Since you’re always giving the odometer reading on the car at each fill-up (be it ‘partial’ or ‘full’), the data is always correlated and self-contained. There’s no need to distinguish between partial and full fill-ups, because you’re always telling the program how far you travelled since the last gas stop…


  8. @Tim – It doesn’t matter if the fill-up is partial or not, but it is important to replace the fuel you have used since the last time you wrote down the mileage. In order to track your “gas mileage”, you need two numbers; the distance you have driven and the amount of fuel you have used. You can get the mileage from your odometer (or trip meter) providing you know the mileage at some point in the past (the last time you got gas, for example) and you also need to know the amount of fuel your vehicle has consumed for the period you have mileage information.

    If your car holds 12 gallons and you normally can go 240 miles between gas stops (full tank each time), your car gets 20 miles/gallon (240/12=20).

    If you only put in 6 gallons at the fuel stop, then the math (240/6=40) tells you that are getting 40 mpg. Obviously this is wrong. The problem with this method is that we have very inaccurately measured the amount of fuel consumed during our 240 miles driven.

    It doesn’t really matter how much gas you get at the fuel stop, it matters how much you have used since during this mileage period.

    A full fill-up is just the easiest and most accurate way to measure the gasoline consumed.

    If you really wanted to be accurate, you would fill-up, drive until the vehicle runs out of gas (to ensure you have consumed all the gas) and do the math on those two numbers (gas & mileage). It’s more accurate, but less convenient. :-)

  9. @tim – The only way for the app to know how much gas you actually used is to tell it how many gallons it took to fill the tank. Partials let you continue to track gallons put in until the next full fillup when the app can calculate how much gas was actually used.

    @David – MyMileageTracker is another web app to look at. Of course, these don’t work if you are on a road trip and stop where there isn’t cell coverage. Just have to write it down in Notes I guess until you find an Edge or 3G connection.

    @Galley – I tried VehiCal, but I didn’t care for the interface. I couldn’t figure out how to delete entries in the trip log, for example.

  10. I’ve been using AccuFuel for the past couple of months and definitely love it. In the latest version, though, this ‘partial’ fillup came into existence, and I’m not sure how to use it…

    By my reasoning, it shouldn’t matter whether a fillup is ‘partial’ (ie-not a full tank) or ‘full’ (from near-empty to the top, I guess), provided the corresponding odometer readings were entered correctly. Also, isn’t *every* fill a ‘partial’? You probably had some gas in the tank in order to get the car to the station…