I think this is really a non-issue. Not sure how RX8Rider arrived at his numbers, but maybe he should replace his Palm with pencil and paper. :D Or maybe a pocket PC.

Well, if you do that on I-95, watch out for all the idiots out there. I try to avoid that road if at all possible. Especially leading into and out of DC in either direction.

 

I'm pretty sure you're right. In my 12k miles, I've trip-metered every gas tank and log it in an Excel spreadsheet. I also write down the odometer reading at the end of every tank and compare that to the cumulative trip-meter total (to make sure I didn't goof somewhere)... and after 12k miles I think my two totals differ by .4 miles, which I'm sure is my own error.

 

True on the non-issue. I assumed that was the case, just a bad Palm program or even operator error. And you're right on the pencil/paper method - that's what I use to record my data, a low-tech 99 cent notebook. :D

You are SO right. I've lived in Northern Virginia most of my life, and I know which roads to avoid and when. I live near the Springfield interchange where I-95 and the beltway meet (locally referred to as "the sausage grinder" or "malfunction junction.") The truckers refer to the beltway around DC as "suicide circle."

 

I have had the same problem. I currently have 16K miles on my car. I even had started a thread about it.

https://www.rx8club.com/rx-8-discussion-3/odometer-measurement-miscalculation-37681/

 

In that thread, you indicate that the error was about 5 mile in 100 miles. Did you drive 100 miles without getting off the road or is this an extrapolation from a shorter distance? My initial runs using GPS indicated a similar error, but my recent mile-marker runs indicated a much lower error rate.

BTW, the intial poster in this thread was reporting a disparity between the trip meeter readings and the odometer readings. My testing did not show that disparity.

 

Okay, I got the chance to do a mile-marker comparison on my odometer on I-95, average speed 75 mph:

Mile marker distance: 34.3 miles
Odometer distance: 34.2 miles

Here, the worst-case scenario (that the odometer was off by exactly 1/10th of a mile) is that it was off by .0029, or less than 1/3 of 1%

I'm content.

 

Interesting Paul. My error (.005) was not that different from yours except that it was in the other direction. That is, more miles on the odometer than the mile markers indicated. I suspect that the placement of the "standard" mile markers is not very precise. I recall seeing some areas on Interstates that were intended for odometer testing and placement of those markers is probably very precise. (Can't remember where that was, however.)

I think it's safe to say that our odometers and speedometers are about as accurate as Mazda could make them.