SINOTRACKGPS Speedometer for Car Universal MPH Speedometer

Added it to my RV dash as my speedometer is hard to read under certain conditions. Appeared to work well until I compared the reading with several other sources. It reads 3mph high at 65mph. The display also quit after it was in the sun for a few hours which means I can't place it in an area of easy viewing.

my factory cluster doesn't always work so I Purchased this speedometer and when my cluster flickers on the speed reads the same

mo where close . returned

Takes to long to start working. When it does its acceptable

I picked this item to put on my lawnmower just for fun and because I'm one of those people who finds mowing the grass kind-of boring. I had to test it first of course.I took it on a test drive with my wife driving over about ten miles. From never having been used, it took about one minute to acquire the satellites and start to display the speed which is definitely not bad in my experience (though there is no way to see how many sats acquired or the estimated accuracy). Sadly, things didn't go great from there. Compared to the Maps app on my phone, the device read consistently approximately 10% high over the course of the trip at speeds ranging from 20mph up to 55mph.I know GPS isn't a precise technology but that means you would expect to see fluctuations above and below the compared speed and much smaller but this was consistent. I just don't understand how the math would be that wrong.Some might suggest that the Maps app was reading slow but it was consistent with the known errors on my wife's speedometer and that has been consistent (in error) with other GPS devices. Sadly, there is no adjustment.Some *have* suggested this is set high deliberately so that claims cannot be made that it lead to one speeding. Perhaps. But it's off so far that it really falls into the not-reliable realm.Still, I guess it will be OK on my lawnmower at 3-5mph. I'm not that impressed though.