One year (lifetime) MPG chart

I've graphed my mpg from the day I bought it, and I find it interesting. It graphs roughly a year, starting in Dec 2004/Jan 2005. Visually, you could see it as approximately 2005 from one winter to the next, with summer in the center.

1) The dots are the fillups (about weekly) and show a lot of variation, owing to the uncertain fillup volume in any given tank.

2) The dotted green line is on the right-hand scale, and shows the cumulative mileage driven.

3) The pink line is the cumulative mpg since purchase. The break-in effect can be clearly seen as an improvement from 40mpg to 43/44 after 5,000 miles.

4) The most interesting line is the black line. It represents a 4-period running average, roughly a month's worth of driving averaged. Keeping in mind I live in SoCal, the optimum mpg is clearly in the spring and fall. Summer and winter take a small hit of 1-2 mpg. In the summer, this can be attributed to the use of A/C, and in winter to the longer ICE runs to stay warm. I would expect colder climates to have a pronounced winter drop, and hot climates a larger one in summer.

By the way, my last few tanks have shown 47mpg in the MFD, vs 45 as calculated here, a 4% error on the optimistic side.

In a couple of months, it will be interesting to see if the SSC 40P programming has an effect. I can't tell yet; the battery was down to 2 bars when returned to me, and I spent a lot of time at a car wash and in ready mode "idling" with occasional ICE runs, making this tank a poor measure.
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