I'd be interested to see a plot of mpg by month across each car model (better still by reported temperature). I'm running 10 mpg worse in the cold than I was in the spring / fall.

 

Cold weather kills my MPG.kevin

 

The old database used to have an option to show temperature. Not sure if the new one does. For individual cars you can see the month to month.

I don't think it makes sense to chart it for the whole model since people live in different areas and have different temperatures it would throw everything off.

On the other hand If Jason wanted to I think he could do a temperature graph to show the average MPG for that car for that temperature. So maybe it would work.

 

The old database showed this phenomena perfectly because it wrapped around and showed the months. I've asked to have that feature restored. Mileage is highest when the temp is the warmest you can stand without AC. AC reduces mileage but not as much as rain or cold. Mid winter tanks are always the lowest. For early and late summer are the best times for max mileage. AC kills mid summer for many. Hard core hypermilers get their best mileage on the hottest days by driving sans AC. I hit almost 40mpg in my black Vette mid summer by not using AC.... and yes, it sucked BTW.

Side note:

If you are gonna try and max out your mileage by keeping the AC off, get a silver or white car, not a black one!

 

There are some technical reasons preventing the full implementation of such features. In version one of the database, I never thought to add multi-year options so Jan 2004 and Jan 2005 would both be displayed under the same January category. With millions of miles already logged, there was no way to separate them afterwards.

Now I could easily split things based on when tanks were added, but the add date doesn't necessarily correspond to the month the tank was driven in. So, there's another problem.

Lastly, I could incorporate temperature into the graphs, but there are so many confounding variables (user error, estimation/rounding of each entry, climate, location, driving habits, etc.) that any temperature-mileage relationship won't be nearly accurate. It will only show that at times they can have a relationship. And, there's no way to compare car-to-car.

 

Generaly I think people would add their milage shortly after filling. But at any rate you could always add a drop down for month of the tank so people could select which month they want it counted against.

What about just having a seperate table that just shows mpg vs temp and not put in months? Sure the temp is arbatrary, but it should be good enough to get an idea.

 

Actually, you'd be surprised how many people add their car along with 2 years of tank-by-tank data. There are also many who wait until they have several tanks to add before editing their car. And, of course, a tank that ends Dec 1 should count for Nov. There are just too many variables for me to add this sort of feature with any reliability.

As far as temperature, it's a possibility, but again I'm hesitant to publish data that is knowingly inaccurate.