Is your speedometer lying?

[Mr. Left]

I have the 2009 Mazda 5 GT for 3 weeks now and today I compared the speed indicated on my GPS to the one shown by the speedometer. Looks like the speedometer indicates the car is going 105 km/h when the GPs shows only 100 km/h. 5% is a lot, I will rake the milleage on the odometer faster than normal, with all the issues that come from this: depreciation, out of warranty faster... Please check your readings and let me know if you experience the same problem.

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[shipo]

Originally Posted by Mr. Left

I have the 2009 Mazda 5 GT for 3 weeks now and today I compared the speed indicated on my GPS to the one shown by the speedometer. Looks like the speedometer indicates the car is going 105 km/h when the GPs shows only 100 km/h. 5% is a lot, I will rake the milleage on the odometer faster than normal, with all the issues that come from this: depreciation, out of warranty faster...

Please check your readings and let me know if you experience the same problem.

Due to the idiosyncratic way the laws that govern vehicle odometers and speedometers are written, many car manufacturers have speedometers that are optimistic while the odometers are spot on. If I recall correctly, both Canada and the U.S. laws state that the speedometer has to be within 7%, however, the odometer has to be within 1% (or something very near that point).

As a suggestion, use your GPS to calculate the kilometers driven and compare it to your odometer, my guess is that you'll find them to be pretty close.

[GSX600FMAN]

The same goes for the UK with respect to speedos. My 2008 Mazda5 sport shows higher on clock than on GPS's (stand alone Pocket PC based navigation with different receivers). for example clock says 140 GPS says 127. This is for various reasons I wont bore anyone with.

[NickC]

That can't possibly be MPH......I thought the 5 was restricted ;-)