Question about Gas Apps

[thebiggoose]

With apps such as MPG, Mileage Tracker, Miley, and more, plus a bevy of web apps here and more coming, I have a question. So the apps have me input the fuel amount purchased, fuel price and odometer/tripometer reading. My question is, how do the apps know how much gas is left in my fuel tank, or is that not necessary. Are they assuming that every time I get gas I am on completely empty? How do I work this out? I'm sorry if I am not phrasing my question right.

Thanks!

 

[BobF4321]

Real-time car info

I would like to see an app that reads data from the car in real-time and calculates gas mileage, etc. No need to enter data manually!
Here is one for the Nokia N800 that I have used:
http://openbossa.indt.org/carman/
It reads the data via a bluetooth OBD-II device that you plug in under your dash.

 

[TonyHoyle]

It's not necessary.. they only need to know how much fuel you bought and how much mileage you got since the last refill.

eg. if you buy 10 gallons a week and go 300 miles each time that's 30mpg. The size of the tank really doesn't matter in that case.

 

[ElecEagle]

Any mileage application should provide the ability to differentiate between a partial fill and a full fill. If they don't, they won't be very useful.

I purchased "CarCare" from the app store and have already been in contact with the developer on a few bugs and suggestions. His next version (due this week, I think) will have the partial / full fill option.

 

[atomheartmother]

It's not necessary.. they only need to know how much fuel you bought and how much mileage you got since the last refill.

eg. if you buy 10 gallons a week and go 300 miles each time that's 30mpg. The size of the tank really doesn't matter in that case.

The only problem is that most cars don't tell you (with any accuracy) how much fuel the car has consumed. For example, it won't tell me that it has consumed 10 gallons. So basically, I'm left with just looking at the gauge. For example, "I put in 5 gallons, it went from a quarter tank to a half a tank, so I will enter the odometer data when it gets back to a quarter tank." However, that is inherently flawed as most gas gauges make small incremental changes. I could go maybe 15-20 miles or so (or more) without making noticeable changes in the gauge; moreover, even small changes in the gauge could mean many miles.

So, in essence, I could be 30, 40, or more miles off, which will change the MPG considerably.

Anyone know any other solution?

 

[diamond.g]

The only problem is that most cars don't tell you (with any accuracy) how much fuel the car has consumed. For example, it won't tell me that it has consumed 10 gallons. So basically, I'm left with just looking at the gauge. For example, "I put in 5 gallons, it went from a quarter tank to a half a tank, so I will enter the odometer data when it gets back to a quarter tank." However, that is inherently flawed as most gas gauges make small incremental changes. I could go maybe 15-20 miles or so (or more) without making noticeable changes in the gauge; moreover, even small changes in the gauge could mean many miles.

So, in essence, I could be 30, 40, or more miles off, which will change the MPG considerably.

Anyone know any other solution?

But the gauge doesn't have to be accurate as you are telling the app how much gas you put in and at what cost. The point behind the odometer reading is to get your mpg. The MPG should get more accurate the more times you fill up as it can take averages of all trips entered.

It isn't going by gas gauge as most of them aren't accurate. The only true way to tell how much gas you are using is to glean injector duty cycle and size and mathematically calculate how much gas you are using at any given point in time. From there you would have to figure out how long it would take you to empty a tank and how far you went and a bunch of other things. For those people that have cars that tell then DTE or MPG they have no real use for the MPG programs as the car does all that for them.

 

[atomheartmother]

But the gauge doesn't have to be accurate as you are telling the app how much gas you put in and at what cost. The point behind the odometer reading is to get your mpg. The MPG should get more accurate the more times you fill up as it can take averages of all trips entered.

It isn't going by gas gauge as most of them aren't accurate. The only true way to tell how much gas you are using is to glean injector duty cycle and size and mathematically calculate how much gas you are using at any given point in time. From there you would have to figure out how long it would take you to empty a tank and how far you went and a bunch of other things. For those people that have cars that tell then DTE or MPG they have no real use for the MPG programs as the car does all that for them.

But then you'll need to run your car down to the fumes. If I never let my car get below, say, a quarter tank, there is no way I can get an accurate measurement. Though, I suppose it should average things out over time.

 

[diamond.g]

But then you'll need to run your car down to the fumes. If I never let my car get below, say, a quarter tank, there is no way I can get an accurate measurement. Though, I suppose it should average things out over time.

Not really. As Injector Duty cycle dictates how much fuel your vehicle is using for a particular throttle position, you should be able to take that rate (say 370CC/min @ WOT) and divide (or multiply I forget) that into your fuel tank size (which is found in your owners manual or online). That should tell you how long it would take your tank to go empty. Record your speed for that particular rate (say 100MPH) and multiply that by how long it would take for your tank to go empty. That should give you DTE and estimated MPG (just divide by tank size).

Of course unless you have a way to get the live data (say from ODB) the whole injector duty cycle calculation is impractical.

 

[JNB]

Gas gauges are for quantity as a relative percentage of "full," not a precise numeric measurement of used/remaining. That's why the meter reading on the pump is what's used to calculate mileage, regardless of how much is or isn't in the tank. If you let the pump fill to the automated stop and quit there every time, then that amount divided into the miles since the last fill as measured on the odometer will give you an accurate mpg calculation, for the most recent quantity used.

Variables include the pump's sensitivity to the "stop point" and whether your tire/wheel combination is within the manufacturer's original spec. Final circumference changes will alter the odometer (and speedometer) readings. Assuming everything's copacetic, the best accuracy you could hope for in any event is to within about a tenth to a quarter mile per gallon.

 

[twoodcc]

to calculate gas mileage, you do not need to know the tank capacity. but no matter how much you use, you must fill the tank up to be able to calculate the mileage. so you get to half a tank, and you put in $10, you won't get an accurate reading. (or you can't calculate anything)

 

[amysig]

no wonder there are multiple gas mileage calc apps...I didn't think this was a complicated problem.

 

[Sphyrna]

Which gas app do you guys recommend? There's quite a few and I wasn't sure which is the best.

 

[Galley]

My MileMarker has a web app that's very good, and is free.
http://mymilemarker.com/m

 

[kis]

Perhaps the programmers of these gas apps should start to realize that the iPhone is sold outside of the US as well. Hardly anyone uses the old English system anymore except for the US (not even the British...) - can someone add support for the metric system to one of these apps, please?

 

[ucfgrad93]

^^^^^AccuFuel has support for liters/kilometers.

 

[fsartono]

I've tried GasHog, CarStat, and AccuFuel and I'd say AccuFuel is the best looking (love the summary chart page), easiest to use (love the type of car selection and data entry).

I'd like to see the following features in the next AccuFuel version:
- Field to enter brand of fuel (ie Shell, Esso, etc.)
- Field to enter type of fuel (ie Shell F95, Shell F98, Esso 5000, 8000, etc.)
- Field to enter driving mode (mostly city, mostly highway, etc.)
- Field for free entry (ie notes, and other infos)

Then I'd like to see another summary page that has pre-summarized info such as:
- Your most fuel efficient fuel is Shell F98 (for example)
- In the city, your average mileage is ...
- On the highway, your average mileage is ...
- In the last month you have spent $XX on fuel
- Your average monthly fuel consumption is $xx
- Your average monthly distance is yy-km

 

[TEG]

I don't understand how hard this is, and why anyone needs an app to calculate efficiency.

Simple Process
1)Fill Tank - Set Trip Odometer to 0
2)Drive
3)Fill Tank - Record Trip Odometer Value then set to zero
4)Divide Odometer Value by Gallons used to fill the tank in step 3 (from reading right off the pump or from the reciept). The Value given if you Fuel Efficiency.

If you can't fill up, but need more fuel, then don't reset the odometer, but remember the number of gallons purchased and add that value to the ammount of fuel purchased when you fill up next when you do the step 4 calculation.

TEG