What is the Most Accurate Way

[Brian R.]

to measure the distance you travel while driving?

Odometers are notoriously inaccurate.

Mileage markers? How were the placing of mileage markers on highways determined? By an old fart in a pick-up truck with his odometer? Every time it hit a 0 in the tenths, he dropped a stick out the window?

This is important!

[dZeus]

a palmtop loaded with gps software + receiver?

[Wombat]

Odometers are notoriously inaccurate?

[Brian R.]

Will that give you actual distance traveled along a curved path? or only the line of sight distance between two points along the route?

[Brian R.]

Originally posted by Wombat
Odometers are notoriously inaccurate?

That's the word

[dZeus]

Originally posted by Brian R.
Will that give you actual distance traveled along a curved path? or only the line of sight distance between two points along the route?

afaik, there's software to do that (along the travelled path). TomTom maybe? (I don't have first hand experience with it)

[Helevitia]

My GPS works really well

My odometer is off because I have bigger tires on my truck. My GPS gives me much better accuracy.

How accurate do you want it to be?

[Fluff]

My Tom Tom reads 30mph and the speedo reads 34mph.

Odometers are probably with tolerances of +/- 10%

Also Trip computers are probably quite inaccurate. when they determine mpg.

I wonder how accurate gas station meters are? I wouldn't be suprised if they were designed to be calibrated to the low end of the tolerance for 1 gallon of gas.

[KRSESQ]

I don't know who's in charge of calibrating gas pumps across the pond, but around here gas pumps are inspected annually by the Public Service Commission, whose requirements for accuracy are quite stringent.

Public Service Commission members in North Dakota are elected rather than appointed, so charges of cronyism and corruption are minimized and public accountability is maximized.

As long as the tire size for your vehicle is correct, the speedometer and odometer should be accurate to within 1 or 2 percent. If you have odd size tires, all bets are off.

At least, that's what my owner's manual says.

If you can find a garage with a dynamometer, I'm sure they'd be willing to test it for you, for a price.

Kevin

[Brian R.]

Originally posted by Helevitia
How accurate do you want it to be?

I was thinking in the range where you can accurately determine your gasoline mileage to say +/- 1.0 mpg or about 4%. If the error in the gas pumps is too high, I guess that's not possible.

As far as the accuracy of odometers go, a guy I was talking to said his workplace was either 27 or 31 miles from his home depending on which of his cars he drove, both Toyotas. That's a discrepancy of somewhere around 15%.

[Greebe]

Gasoline meters are calibrated at set volumes. That being said there was a scandle not so many years ago where these were intentionally calibrated to read more at anything but the standards ie if you were to measure out 1, 5, 10 gallons it read properly, but if you measured out anything other than these amounts it would always give you less gas. If memory serves me correct there was several chain of gasoline stations busted on this in California along with the companies who supplied the altered metering controls.

[KRSESQ]

Also the temp of the gasoline has to be taken into account. Gasoline expands quite a bit when warm, so even if the pump accurately meters out one gallon, you'll still be getting less gas than you would if the gas were cold.

Most gasoline storage tanks are underground, though, so the temp is reasonably constant throughout the year.

Kevin

[Fluff]

Just looked at the UK regulations. It allows for a +/- 60ml error in 12Litres of fuel which is pretty stringent.

I'm not sure if the wheels for my car (peugeot)are the original shipping ones or whether the previous owner bought some new peugeot alloys which were a slightly different size.


On fuel temp there is this study..

http://www.nel.uk/upload/pdfs/warm-fuel.pdf

[GNEP]

Reminds me of the endless discussions we have with our operating companies in different climates on how much volume they sell... correcting to STP conditions is not a concept most accountants who actually record this stuff understand

But hey, when I work in kbbl/day at best what do I care about the odd gallon here or there

[Jon P. Inghram]

The odometer on my ratty old '87 Cavalier was dead-on accurate (verfied via GPS,) at least until I bought new tires that had a different profile. Now it's off a few percent, at 65 MPH it reads ~63 for example.