Thursday, June 28, 2007

To and From Work in a Minivan

Yesterday I had the opportunity to take our green minivan to work so it
could get two new tires. We're taking the green minivan on a road trip
over the upcoming long weekend, and one of the front tires was very bald
on the outsides.

I filled the tank with gas from Costco (less than 1.5 miles from my
home), and drove sensibly to work. The trip computer indicated 29.4 mpg
on the trip. There's another costco about 0.75 miles from my office, so
I drove it over there for the new tires and walked back to work as that
was in process.

My trip home was about normal for a Wednesday, taking 56 minutes.
During that time, the trip computer's average mpg went down from 29.4 to

It appears that mileage is substantially lower on my trip home. This
must be due to the increased stop-and-go traffic on the Interstate. I
tried coasting as much as I could, and was gentle on the accelerator,
yet the mileage was nowhere near what it was on my trip in to work. It
must have been closer to 20 or 21 mpg to bring the average mileage down
by so much (using simple estimation that my commute to and from work is
about the same distance).

So the conclusion is that my behavior on my trip home is much more
important in maintaining decent fuel economy.

It is clearly critical to have a good view of the road, what's ahead of
you, and traffic conditions around you so that you don't waste precious
gasoline accellerating into a spot where you'll just slam on your

Wednesday, June 27, 2007

Minivan Mileage vs. Trip Computer

We have a green minivan that has a trip computer in it that, among other
things, tells us our average fuel economy, current fuel economy, and
time in the car with the engine running. We usually reset these
functions at each fill up.

The van needs two new tires, so I drove it to work this morning to drop
off at the tire store. But first, the van needed gas. So I put in
16.075 gallons at our local Costco, at $2.699/gallon, the same price as
earlier this week. The van had gone 254.0 miles, making for 15.80 mpg.

The trip computer indicated our fuel economy for this tank was 16.4.
About a 4% difference in numbers. If I stopped the pump after the first
click, mileage would have worked out to be 15.98 mpg, still lower than
the trip computer.

Almost all the miles we put on the van are "around town" miles, trips of
less than ten miles, and frequently less than five miles. There are
times we go three weeks between fill ups, so I guess 15.8 is okay for
this sort of driving in a minivan.

The trip computer showed fuel economy of 29.4 mpg for my commute to work
this morning in the very same minivan, but with the 4% error, my mileage
may be as low as 28.32 mpg for the trip.

Monday, June 25, 2007

Tank 121 - 25 June 2007

Achieved 38.01 mpg on this tank, raising my overall average for 2007 to
37.13 mpg. If I stopped at the first click of the pump, my mileage
would have been over 39.

I traveled 427.2 miles on 11.238 gallons, at a cost of $2.699 per
gallon. Last year at this time, gas was nine cents cheaper per gallon.
This tank cost me $1.01 more than it would have at the end of last June.

Since I pumped my tires up to 40 psi, I have not really noticed a huge
increase in my overall mileage. Perhaps it is because we are using the
mighty Corolla more on the weekends for local trips in town.

I actually went about 30 miles around town on Friday and Saturday,
taking the kids to and from camp, and to the grocery store. The low
fuel light was on the entire time. I was quite concerned that I might
not make it to Costco this morning to fill up.

Actually, there have been 21 tanks that have needed more than 11 gallons
to fill up, and today's was the ninth most gas I have ever had to put in
the car, and the seventh highest total of miles per tank (four of those
seven, and six of the top ten, happened this year).

I should be able to go all this week without filling up, and will be on
a short vacation early next week. I may not need to put gas in the car
again until July 9, which would tie the longest stretch of time between

Thursday, June 14, 2007

Tank 120 - 14 June 2007

Filled this morning at the Woodbridge Costco again. 410.1 miles on
10.916 gallons, making for 37.57 mpg.

I knew this would happen for two reasons. First, my mileage almost
always goes down the tank right after a "great mileage" tank, say 39 mpg
or higher. Second, we used the Corolla for two days of family jaunts
around town over last weekend.

I think this tank would have been 38 mpg or better had it stayed in the
garage over the weekend.

Still, 37.57 is better than my overall average of 36.33, and better than
my 2997 average of 37.09.

Interestingly, it was just about one year ago that I managed my best
mileage ever, 41.06 mpg. The tank right after was 36.13 mpg, a drop of
4.93 mpg. This tank's drop of 2.24 mpg is half that.

Gas last june 12 was $2.729 per gallon, the exact same price I paid this
morning, 367 days and 17,146 miles later.

Monday, June 11, 2007

Weekend Family Travels in the Mighty Corolla

We took all the family trips Friday and Saturday in the Corolla. The
five of us took it out to lunch, to a free car wash, and to a weekend
"block party" sponsored by the local radio station.

The good news is that in town, the Corolla probably gets double the
mileage of the green minivan we usually use.

The bad news is it'll probably lower my overall mileage number for this
tank, since most of the time the Corolla is just used for commuting on
the highway, and maybe one local trip over the weekend.

An episode of Mythbusters yesterday studied drafting, and it showed that
mileage improves even if you're 7-10 carlengths behind a tractor

Mileage is even better if you can go 55 mph rather than 65 on the
highway, but that causes more of a traffic backup and wastes more gas
overall (due to all those other cars braking and speeding up to pass and
braking again) than one car's savings can justify.

Wednesday, June 6, 2007

Tank 119 - 6 June 07

39.81 MPG. I went 420.8 miles before the "low gas" light turned on, and
431.3 miles total, when I filled with 10.833 gallons at the new
Woodbridge Costco.

Gas was $2.919/gallon.

This is the first tank since I pumped the tires up to 40 PSI, which
occurred about 90 miles, or about 20% into this tank.

Historically, however, the tank after a high-mileage tank tends to be
lower than average. This is a problem that at first seems related to
the amount of gas that gets pumped each tank, but I always pump it the
same, "one more click after the first one."

Another odd thing I have noticed is that if you add up the total trip
odometer readings, they total 42,994.3 miles. But the car's master
odometer reads 43,035. Somewhere there is a glitch. I noticed this
problem last year as well, but have yet to do anything about it.

I read an article about erroneous odometers and that Toyota was
extending warranties because of it, but a difference of less than 100
miles over 43,000 miles seems acceptable, I guess.

Tuesday, June 5, 2007

What if I Attach a Picture?

Sometimes I update this blog via email. When that happens, there are
usually some errors that show up, like line breaks at unusual locations.
I think this happens because my email program only sends things in plain

I am attaching a picture to this one. At the other blog I used before I
started this one on "blogger," I think an attached picture showed up in
the body of the post.

We'll see here.

If this doesn't work, maybe there's another way...

Gas tank and mileage update will likely come tomorrow.