Mileage discrepancy between odometer and GPS

i think toyota wants you to run out of warranty before you actually arrive.

 

2% error. Honda lost class action lawsuit on 5% error in 2007.

 

I think your test distance is too short to draw any conclusions. You need much more data. When you get a 100-200 mi. trip the error will have more meaning, and if you do it 3 or 4 times and get the same results you can start believing the numbers.

 

Not always.

Most vehicles have speedometer error built in. Motorcycles have it because of variations in gearing and tire sizes, but it's often 5% less than actual. The "SpeedoHealer" is often installed to let you mathematically correct the error. You don't need miles to figure it out. Just a couple 1 mile runs with a GPS. GPS vs. odometer + formula = correction factor.

Cars should be spot on if you get the OEM setup from the factory (higher trim level wheel change sizes WILL alter odometer/speedometer readings because the system is calibrated to the stock wheel/tire size intended for the vehicle), but I'd not be surprised to find they still have errors.

 

Right, but the OP is taking about ODOmeter.

 

If the spedometer reading is off, so will the odometer. Both use the same sensor.

 

Different calibration. There are laws on allowable speedometer calibration errors, but not on odometer calibration.

 

The elephant-in-the-room is the well worn 17" tires, I assume 215/45R17.

I've often wondered if Toyota adjusted the odometer to account for the difference in OD of the 17" tires. Maybe not??

BTW, we also have the 17's on our Canadian "Touring" model.

This is my tire calculation spreadsheet, just using the stated sizes. I entered the 15.9 miles in bold, and the bold value to it's right is 15.9 times 0.986.

 

When a colleague and I exchanged our Volt and PiP for a week last year we both noticed that the PiP odometer was reporting about 1.5- 2.0% greater distance than the Volt when driven on an identical route. You are reporting a 2.0-2.5% discrepancy between your PiP and your GPS. Specifically, my Volt would report my drive from home to work as 45.5 miles and the PiP would report it as 46.3 miles.

This would tend to exaggerate the PiP's mpg and EV efficiency results much like the Prius/PiP gasoline consumption reported by the car averages about 3% optimistic whereas my Volt reports gasoline consumption that is within 1% of that reported at the pump.

I don't understand why Toyota can't report more accurate averages.

 

Swap your tires for 195/65R15?

 

But do you see my point? The 215//45R17 have a significantly smaller OD, and your's are worn. I'm guessing the odometer of the US Five (and our Canadian Touring model, in the same boat) has not been adjusted for the different tire size. If that's the case, and odo is accurate with the 15" tires, it's going to overreport miles with the 17".

 

And Subaru too, in 2010.

 

Were running 215/45R17 in summer, and 195/65r15 (snow tires) in winter. I suspect our Garmin navigator can display distance travelled? I'll look into it, repeat with the snows, post back. It'll take a few months though, lol.

The one downer: our mileage with the 17's is likely a bit less than calculated. If Toyota hasn't adjusted the odometer.

 

As I already posted, your distance is too short to be expected to be accurate. GPS distance traveled is from point to point as you stated. Turn a corner and you can loose distance if the "samples" cause the track to be across the corner. You don't see it on the GPS screen because it usually "snaps" the track to a road for display. Turn that off and you will see how the GPS points cause the "assumed" path to wander.
Do a test over a much longer distance. There the errors will average out.

As far as complaining about how "inaccurate" the odometer is, please get reasonable. The Prius IS NOT a lab instrument. 2% accuracy is pretty good for such an inexpensive device! Just the wear in the tyres and possibly tire pressure differences can cause greater error.

 

Wrong. Yes the same sensor but the speed includes a calculation which may, or may, not be accurate. And that accuracy may make the reading high but never low.

 

I'm probably thinking of a mechanical setup (even with an electronic sensor). The signal drives both so off MPH will likewise affect odometer readings. All digital could apply different calculations to the same original signal pulse.