Friday, December 28, 2007

2007 End-of-Year Statistics

It looks like I will not be refilling my gas tank until January 2 or 3,
2008, so I can start making comparisons between my 2006 and 2007 data.

2006 - 46 tanks of gas
2007 - 41 tanks of gas (10.87% fewer)

2006 - 462.026 gallons
2007 - 431.259 gallons (6.67% fewer)

2006 - $1,099.90 total cost
2007 - $1,090.30 total cost

2006 - $2.378 average cost/gallon
2007 - $2.529 average cost/gallon (6.36% higher)

2006 - 36.26 average mpg
2007 - 37.87 average mpg (4.43% higher)

2006 - 16,742.3 miles driven
2007 - 16,338.7 miles driven (2.4% fewer)

This is interesting data. My reduction in gallons used, and increase in
fuel economy, pretty much evened out the increase in gas prices.

Even if I refueled today, my total miles driven for the year would be
under my 2006 total. I think this potential for error is eliminated due
to the fact that my first tank of 2006 was on January 11.

I still drive lots of miles to and from work.

But I drive smartly and consistently, which results in fuel economy
higher than the reported EPA ratings, and I do my best to maintain the
car in safe and efficient working order.

Here's to an even better 2008!

Wednesday, December 12, 2007

Tank 140 - 12 December 2007

My theory that the Woodbridge Costco's gas pumps automatically shut off
sooner than those at the Fredericksburg Costco got a real boost today as
I filled up at Fredericksburg this morning and found my calculated fuel
economy to be just 35.65 mpg.

This economy is over 4 mpg lower than my last tank.

My last tank was 2 mpg higher than the tank before that, and this tank
is 2 mpg below that one.

The average of my last 2 tanks is the same as the average of the
preceeding 2 tanks (using my eyeball calculating technique).

What does this mean? Probably that in order to be fair with each tank,
I should refuel at the same exact pump each and every time. In reality
I won't be able to do this too often.

Maybe I ought to track the pump number at the gas station as well, to
see if any relevant data can be gleaned from a few months worth of data
there.

I'm definitely going to need a bigger notepad.

Tuesday, December 4, 2007

Tank 139 - 4 December 2007

This morning I was able to refuel at the Woodbridge Costco. I needed
10.632 gallons after going 424.7 miles, making for a fuel economy of
39.95 mpg. My low fuel light came on at 417.7 miles.

This makes me feel better, coming off of two poor showings of fuel
economy. But I am suspicious that the Woodbridge Costco gas pumps have
more sensitive shut-off sensors. I suspect that if I refueled at the
Fredericksburg Costco, as I normally do, I'd have put in as much as half
a gallon more gas, but there's no way to be sure.

For this reason, I have started tracking my fuel economy for the last
five tanks averaged. This still stands at over 38 mpg, so that should
even out some of the discrepancies inherent in different fuel pumps.

This was my 40th tank of 2007. I have gone 15,937.7 miles on those
tanks this year. Compared with 2006, I went 14,587.6 miles on the first
40 tanks. However, I reached the 40th tank on November 3 of 2006, just
about one month earlier than this year. On a corresponding date in 2006
(December 3), I had gone 15,641.4 miles, similar to this year but still
about 300 fewer miles.

Last December 3, I had spent $1,032.80 on gas. This year, on December
4, I have spent $1,058.93 on gas. Gas has averaged about 15 cents more
per gallon this year, or about 6.1% more. But my fuel economy has
averaged about 4.6% higher, so there's a fair amount of offsetting
there, expense/benefit-wise.

Overall, a good tank of gas.