Personally, my minimum mileage measure is one full tank, but ideally it is four or five tanks of gas. The reason is, depending on a number of factors (of which, climate is only one) one could easily fill up 1/2 gallon differently than last time, or one could drive differently, or one could do many things differently, that would impact results either way. The more records of gas mileage that you have, the more accurate the figures will be. They'll never be totally precise.

I have seen some awful mileage figures, in the 15mpg range, and I have actually seen 32MPG out of my 940 wagon. The 32MPG figure was coasting along at 60mph, no bikes or racks on the top, no A/C, very few hills.

While I love 32MPG, I have a life, so to avoid acquiring additional gray hair while driving, I usually dig into the gas and deal with the price.

Driving across the country in my Avalon, 33mpg was my "standard" mileage. Despite driving upwards of 90 at times, I never saw under 30mpg, ever. The A/C cycled on and off periodically over the trip. I'm convinced I could have pulled 35mpg traveling the speed limit over the entire distance, but I lack the patience. I'd rather be home in my own bed than spending an extra night in a hotel. That said, driving around Scottsdale with its lead-footed drivers and ample supply of stoplights, I rarely see 20mpg. Then again, since I buy maybe $30 in gas per month and sometimes only fuel twice per month just to get the car wash/gas discount (I don't commute) my MPG figures are not very reliable.

As they say... "Your mileage may vary". My point is, your mileage is not bad given that you are basing it from a small measurement. If you measure more, you may find that it improves significantly. Also disregard the coldest and hottest temperatures, plus the times when you sit idle in traffic for 3 hours, because those are not representative of more "normal" conditions. Unless you drive in those conditions every day of the year.

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Chris Herbst
Scottsdale, AZ