Wow – who wouldn’t buy a car that got such great mileage, even if it was a Honda Civic; qnd look at the quality of the “54 MPG” logo on the back of the car – GBMINI has nothing quite like this:
Meanwhile back in the real world, Leslie who runs MyAutoLog has updated GBMINIs fuelling data, to show an average of almost 27mpg since I got my third MINI – a little better than the average MCS, but not as good as the average MC:
Of course MPG is heavily dependant on driving style and traffic conditions, but averaged over 85 MINI Coopers, 289 MINI Cooper S and over 100 JCW equipped MINI Cooper S, I think the “real world” figures for the cars are realistic, showing about 10% better fuel economy for the non-S engine.
I am impressed with all the work that Leslie has done, and really like MyAutoLog, except for one, to me, very significant detail:
In the above data, you can see that on 12/2 I “short-filled” my tank (only putting 10.4 gallons in) prior to a trip – I’d driven 256 miles since the previous fill, giving me an MPG of 24.6.
After the trip, I filled the tank again, putting in 13.976 gallons (tank must have been quite empty!) and, on the trip distance of 397 miles, giving me an MPG of 28.4.
These figures are realistic, matching the typical MPGs for GBMINI#3 – in the colder weather I get below 25 MPG around town, but I can get 28-30 MPG on a run.
However, MyAutoLog allocates the distance driven to the fuel being burned while driving that distance. In one way this is sensible – you link the “miles with the molecules”.
But it gives incorrect tank-to-tank MPG figures – in the example above, my “short” distance of 256 miles is allocated to the normal full tank prior, of 13.712 gallons and giving a much-too-low MPG of 18.67; and then after my trip when I fill up again, the 397 miles is associated with the 10.4 gallons, giving a much-too-high MPG of 38.16!
Leslie & I have discussed this back and forth at length and we both remain on our own side of the fence. Leslie explains that not everyone fills their tank each time, so he never knows how much fuel was really used between fills – that may be true, but then his MPG calculation method is no better anyway, so why not do the correct calculations!
There is one special case where linking the latest fill to the previous one might be sensible – that is if trying to determine the effect of different grades/brands of gas on MPG. But even here, you would have to fill the tank to the same point every time, then you’d need to calculate the MPG based on distance covered since last fill, divided by latest fill quantity, and finally allocate the resulting MPG figure to the previous gas – allocating the distance to the previous fill is not the way to do it.
Of course Leslie points out that, over time, his method and mine give the same averages. True – but my method gives much more sensible tank-to-tank MPGs, making it easy to compare different driving styles / journeys / etc. For example when I drove in a very boring-but-fuel-efficient manner to British Invasion last year, my average got to just over 31 MPG (and the OBC showed 33 for the actual drive up 93N). But Leslies maths makes a claim of over 37 MPG!
Anyway, if you’re interested in your cars average MPG – especially in comparison to other MINIs and other cars – check out MyAutoLog, but don’t rely on the individual tank MPG figures (unless you always put the same amount of gas in the tank).
M&I / GBMINI 
I gave myautolog a solid chance when you featured it last year, and I too was perplexed that he was averaging the milage over the wrong tank of gas and discussed it with him. It means that the report of every tank is wrong, and your final average, while practically being the same, is still off by one tank.
I use bostongasprices,com/gasbuddy.com to do my gas logging, and it does the averaging properly and gives me nice charts, as featured here on my gas page.
Hello Josh. I won’t get into the detailed explanation here, but MyAutoLog.com calculates MPG with the correct miles traveled. Quick example, you fill up with 12 gallons on 2/1/2006 and your odometer reads 1,300 miles. You drive until 2/8/2006 when you fill up again with 10 gallons and your odometer reads 1,600 miles. The MPG can now be calculated for the 2/1/2006 fueling because we know you traveled 300 miles. Just review your fuel logs to see.
I’ll admit the charts on GasBuddy.com are nice and one day I hope to develop them for MyAutoLog.com, but this is a one-man operation. I have to prioritize my free time to develop this stuff and up to this point I’ve had more demand for trip mileage tracking and a mobile version (Mobile.MyAutoLog.com). I like the charts though.
As for the MPG calculation on GasBuddy.com, it is inaccurate. It makes assumptions and is loose which negatively skews the data. Here’s the issue. When you fill up with 12 gallons and then drive for awhile before refueling with another 6 gallons, how do you know exactly how much of the 12 gallons was burned? In order to get a completely accurate MPG calculation you have to measure the fuel still in the tank before refueling. Well, we know that’s not going to happen for your average driver.
To try to solve this problem, GasBuddy.com asks you if you filled up or not. If you fill up every time then it is somewhat accurate (gas pumps have different stopping points, can be adjusted, and could be off as much as a gallon). If you don’t fill up everytime, then it gets really inaccurate. Under GasBuddy.com’s model, you can designate that you didn’t fill up your tank in back to back fuelings. Well, this scenario causes inaccurate MPG results. GasBuddy.com no longer knows how to divide the “missing” fuel over two fuelings. GasBuddy.com also allows you to skip fuelings. I don’t even want to consider what that will do to your fuel mileage.
The bottom line is GasBuddy.com is trying to offer these fuel logging services to provide another incentive to get you to save your fuelings because what they really care about is the cost/gallon of your fueling. The primary goal of their website is to let people know what the gas prices of stations in their area. It’s a great service that lots of people find useful.
For MyAutoLog.com, I want to give people the ability to log their fuelings but the primary goal is to allow a member to compare their vehicle’s fuel mileage to other vehicle classes, makes, and models. So visitors to GBMINI.net would be interested in comparing their MINI’s MPG against all MINIs (MC, MCS, & MCS JCW). Let’s say a member wants to see how their MINI compares against a Mazda Miata and Ford Focus, they can do that. They can compare it against a Hummer or the entire SUV vehicle class. I take great care to make sure the data collected and calculated is correct since it is used collaboratively.
On MyAutoLog.com, the MPG calculation for an individual fueling is inaccurate in certain scenarios and can be confusing. With that said (and my conversation with you and Ian), I have lessened it’s availability on the website. But the same can be said for GasBuddy.com and many other fuel mileage applications I have played with. As with GasBuddy.com, you can still get a fairly accurate MPG for an individual fueling on MyAutoLog.com if you fill up every time you hit “E”. Of course with GasBuddy.com, you should also fill up at the same gas pump at the same gas station every time too.