The problem with not keeping official records is that it's too easy to lose
a receipt, or to include something you shouldn't, such as a partial fillup.
You also can't include the fillup amount from the *start* of your recorded
A written (or Excel) record is more rigorous and more likely to be
accurate, although your recorded 27-28mpg seems right for your car. I get
about 28mpg in my Integra with lots of 80mph highway driving. Not bad for
267,000 miles, huh?
I don't understand your last sentence. Maybe I don't know just what you mean
by the "start of my recorded mileage." By "start" do you mean from the time
I drive it off the dealer's lot? No, I didn't do that.
I fill the tank on my way to work. I note the trip odometer (typically
300 - 320 miles), I have the receipt, and when I get to work I divide the
300 or so miles by the number of gallons bought. How does that differ from
I never based my mileage on one or two samples, even though I'd fill up at
the same gas station. I know that some pumps, and on different days, will
shut off at different levels of gasoline filled into the tank. So I figure
over the course of a couple years I have it down pretty well. ;-)
On 5/18/2006 7:35 AM TeGGeR® spake these words of knowledge:
Actually, as long as you include the *amount of gasoline* you put in,
you will still be able to calculate the correct miles-per-gallon figure,
at your next full fillup. For example, once my tank is full, I start
driving. If I put in 5 gallons, then 11.23 gallons, then 3.99 gallons,
then 8.04 gallons, then do a complete fillup of 14.55 gallons, and
traveled, say, 1611 miles, I averaged 37.63 miles per gallon. Of
course, I can't calculate the MPG for the interim time; only between
"I would rather be exposed to the inconveniences attending too much
liberty than to those attending too small a degree of it." -- Thomas
I'm glad to hear there are people who actually do figure their mileage
properly out there. As I said, nobody I *personally* know (friends,
neighbors, co-workers, etc) does this.
Most of the people I know use the miles per tank method, which is bogus.
I started doing this for business reasons a few years ago
and learned some interesting things. Particularly about summer/winter
driving. My Honda civic has been averaging about 37 mpg
in the summer and 33 in the winter. I think the difference is half
due to winter 15% ethonal (pure ethonal only 70% the mileage)
and other other half due to recreational road trips. I also wonder
if cooler weather on the engines or tire pressure is a factor.
AC has almost now effect.
Depends. If you do a lot of short trips, the engine does run momentarily in
'rich' mode until it is warmed up. The colder it is, the more fuel it will
use every time you start it up.
You should be checking your tire pressure at least monthly. It's not
uncommon to lose quite a bit of pressure going from ambient 80-90 degrees F
to sub-freezing temps. That will definitely affect your mpg.
There was a study not too long ago that found that with modern
automobiles/engines, the A/C used much less fuel than rolling down a window
at speeds above 30mph or so.
Yep. It's in closed-loop as soon as the ECM receives a valid signal from
the primary oxygen sensor, which these days is about 30-40 seconds from a
cold start. But it's still in "warmup enrichment" mode until it sees full
coolant temp, which can be up to ten minutes from cold, depending.
I don't buy it. I don't notice any effect on the car's performance
when I roll down the windows. Turning on the A/C is like throwing out
I just bought a scan gauge monitor that plugs into the OBD-II
receptacle and displays instantaneous milage and a lot of other data.
I will test the window up/down AC on/off controversy and report
My civic is getter better mileage than the published EPA ratings.
Also better than the new Fit EPA ratings.
It is better than my 1990 civic which was smaller and lighter.
I read many people were complaining the EPA ratings to too
good for most cars, especially the hybrids.
On 5/17/2006 8:44 PM TeGGeR® spake these words of knowledge:
I have done it with every fillup since the day I bought my car (2003
Accord LX). I do it with every vehicle I drive, because usually the
first clue that there is a problem is a drop in mileage.
In my book, I record the odometer reading, the per-gallon price, the
total amount I paid for the fillup, and the date. When I enter that in
a spreadsheet, I have (through formulas) the miles traveled, the gallons
purchased, and the MPG for that fillup. Because it was trivial at that
point, my spreadsheet also calculates my total gas cost, the total
number of gallons I have purchased, average price-per-gallon, average
miles-per-fillup, and average cost-per-fillup - over the life of the car.
I have spent $5165.12 in 226 fillups, buying 2945.13 gallons of gas at
an average cost of $1.75.4, averaging 361.65 miles per 13.03 gallon
fillup, at an average cost of $22.85, and an average MPG of 27.75.
If anyone is interested, I can post the Excel spreadsheet with the
formulas still in it, for you to use.
"I have an idea that the phrase 'weaker sex' was coined by some woman to
disarm some man she was preparing to overwhelm." -- Ogden Nash
I've done it on the cars I've owned too. It's just become a habbit. Also
never understood why some people want to keep putting $5 or $10 in the car
instead of filling it up, when they had the money. You'll only have to
visit the gas station that much quicker and more frequently.
Sure! I'd love to put it to use. It would be greatly appreciated.
Y'know, NE Ohio Bob had sent me his Excel spreadsheet, but I never did
anything with it.
I'm now thinking it might be an excellent idea to post any available
spreadsheets as part of a FAQ page. Looks like I've got two potential
contributors so far, and I can post one of my own as well.
If the data are valid, they would serve as an excellent real-world mileage
resource. I could post a raw Excel form, and readers would be free to
download and populate it, then send it to me for posting. Comments?
On 5/18/2006 9:29 PM TeGGeR® spake these words of knowledge:
Sounds like a good idea to me.
I'll send this to you, Tegger, and I'll leave my data in it. Do with it
as you will.
Dave, you can get it from me if you'll email me: dave - at - kelsen -
dot - us, or provide me with a place to send it. I forgot that at the
moment, I don't have a webspace to post it on.
"I have as much authority as the Pope, I just don't have as many people
who believe it." -- George Carlin
Download and distribute as you wish.
THIS is the correct way to calculate mileage, provided each fillup is to
I'll eventually make a new file with clear fields and post it on a new page
entitled something like "how to record your mileage".
What would be excellent is for people to do their own population of the
spreadsheet with their own accurate real-world data, then send the
resulting XLS to me. I think it would make an awesome real-life resource
for gas mileage data.
When I get a moment, I'll transfer my own data into a copy of that XLS and
post that too. Got ten years of data to put up.
Thanks very much to Dave Kelsen. Great contribution.
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