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Do P85Ds and S85Ds have inaccurate odometers that overstate distance traveled?

Andyw2100

Well-Known Member
Oct 22, 2014
6,542
2,443
Ithaca, NY
I believe there is pretty solid evidence that the P85Ds and perhaps the S85Ds as well are consistently overstating the distance they travel. In other words, their odometers are not accurate.

I first noticed this in the excellent side by side efficiency testing that wk057 did. Driving together, parking together, etc., his P85D recorded a greater distance traveled than his fiance's P85 did:
112.2 miles vs. 111.3 miles.

P85D vs. P85 Efficiency Testing - Page 6



I have been recording trips myself, for comparison with EV Trip Planner, and the several different trips I record all result in our P85D claiming a greater distance traveled than EV Trip Planner believes the route should be. Some portion of this is due to the length of our driveway, and my wife having to drive around to park in the parking garage she uses, but not all of the discrepancy can be accounted for this way. Also some of the trips do not involve the parking garage. Some of these trips, which show the discrepancies, are posted here:

P85D vs. P85 Efficiency Testing, Take 2 - Page 17


We've also checked a couple of these (my wife's trip to and from work) against another car (when she doesn't take the Tesla to work) and the other car's mileage figures come out much closer to EV Trip Planner's figures.


In addition to my own trips, I've started noticing that when others post EV Trip Planner comparison data, almost without exception, the mileage their P85D or S85D claims they traveled is greater than the distance EV Trip Planner believes the route was. Below are just a few of those posts:

Real World Comparison of a S85 to an 85D Efficiency - Page 6

Comparing P85D Torque Sleep efficiency (versions .139 and .140) to EV Trip Planner - Page 2

P85D vs. P85 Efficiency Testing, Take 2 - Page 18


Below is a summary of the data from the three posts above:

P85D or S85D
EV Trip Planner
Recorded Mileage
Expected Mileage



53.5
52.8
54
51.7
241
239
100
99.7
156.3
154.1
86.6
85.5
68.4
68.4
149.3
146
If some of you would like to add some data to this thread that supports or refutes this, I think that would be helpful. If it turns out that we collect more data to support my theory that the P85Ds and the S85Ds are overstating the distance they travel, I'll write to Tesla and direct them to this thread.

Thanks.
 

wk057

Vendor & Senior Tinkerer
Feb 23, 2014
6,162
14,876
Hickory, NC, USA
I'll note that this discrepancy was present and nearly identical in both side by side tests I did with my fiance.

Images from Trip 1 -> P85D vs. P85 Efficiency Testing - Page 6

Images from Trip 2 -> P85D vs. P85 Efficiency Testing, Take 2 - Page 6

Video From Trip 1 -> Tesla Model S P85D vs P85 - Efficiency Test, Leg 1 (5x Time Lapse) - YouTube

Video From Trip 2 -> Tesla Model S P85D vs P85 - Efficiency Test, Take 2, Leg 1 (5x Time Lapse) - YouTube

The videos only show the first leg of each test, but the return trip was the same route. The discrepancy is easily noted just from the videos though and it is consistent at around +0.8% on the P85D. That would come to an odometer reading of 100,000 miles on the P85D at only 99,200 actual miles assuming the P85 odometer is the correct one.

I noticed this on my very first trip with the P85D from NJ->NC after taking delivery. The trip meter showed about 6 extra miles vs what I expected from a dozen previous trips on the exact same route.

Honestly, I haven't really had the motivation to bother Tesla about this as of yet.
 

Andyw2100

Well-Known Member
Oct 22, 2014
6,542
2,443
Ithaca, NY
Also, before anyone suggests that it is EV Trip Planner that is off that is causing the discrepancies with much of the other data I referenced, I just checked the four different trip-legs I track data for against Mapquest. For three of the four EV Trip Planner matched Mapquest perfectly (rounding to the nearest tenth mile, which is the accuracy EV Trip Planner shows) and on the fourth trip-leg EV Trip Planner rounded the "wrong" direction, so there was a 1/10th of a mile difference between the two. So EV Trip Planner data for route length matches Mapquest data for route length, at least for the four trip-legs I am tracking.
 
Last edited:

Danal

electricmotorglider.com
My math from all the data indicates about 0.8%, just like wk057. This would make the car 42.something feet off on a measured mile. Those are available all over the place. Let's try it...

And/or GPS cross-check. I have "Agile Speed" iOS app, that includes an odometer. And I happen to be taking a road trip tomorrow. I will try that.
 

gpetti

Active Member
Supporting Member
Nov 6, 2013
1,639
120
Calgary, Canada
I looked at my screen photos from a recent trip and where I had captured the estimated miles from the Nav system I compared them to the actual odometer miles for the leg (driving directly to the supercharger as navigated) and got these comparisons (all Kms for what it's worth)

133 map = 135.6 odo
247 map = 251.2 odo
258 map = 261.1 odo
 

Andyw2100

Well-Known Member
Oct 22, 2014
6,542
2,443
Ithaca, NY
I looked at my screen photos from a recent trip and where I had captured the estimated miles from the Nav system I compared them to the actual odometer miles for the leg (driving directly to the supercharger as navigated) and got these comparisons (all Kms for what it's worth)

133 map = 135.6 odo
247 map = 251.2 odo
258 map = 261.1 odo

That's some excellent additional data. You just demonstrated that the P85D's odometer is not consistent with the P85D's own Navigation system! Thanks!
 

gpetti

Active Member
Supporting Member
Nov 6, 2013
1,639
120
Calgary, Canada
That's some excellent additional data. You just demonstrated that the P85D's odometer is not consistent with the P85D's own Navigation system! Thanks!
NP
Though my numbers strangely seem to show the gap lessening as the Kms go up so there must be some margin of error in my driving.
AFAI. remember I navigated exactly as calculated, though I did drive round a block for one supercharger. Certainly not a margin of 2-3 Kms though.
 

Andyw2100

Well-Known Member
Oct 22, 2014
6,542
2,443
Ithaca, NY
Some of that could be effect of terrain - what is 1km on the map will IRL be slighly longer if its sloped terrain.

from top (map) view, following distances will appear to be the same, despite being different (ignore dots - forum is screwing my formatting):
|-----|

|-
..-
...-
....-
.....-
......|

I'm really not sure what you are trying to say. I think you might be suggesting that EV Trip Planner and Mapquest assume that the ground they are calculating route distances for is perfectly flat. If that's what you're suggesting, without actually researching it, I'm just going to go out on a limb and say you are wrong, and that sites like Mapquest are providing the actual distance a car on the road will travel, including the hills.

- - - Updated - - -

NP
Though my numbers strangely seem to show the gap lessening as the Kms go up so there must be some margin of error in my driving.
AFAI. remember I navigated exactly as calculated, though I did drive round a block for one supercharger. Certainly not a margin of 2-3 Kms though.

If it was the last one that you drove around the block for, your other two sets of numbers are similar, though more than double .8%.
 
A few weeks back I did a quick eyeball test because I suspected that the odometer was off on my P85D. I reset my TRIP A odometer at the moment I passed an interstate mile marker. 15 mile markers later, my trip odometer was at just over 15.3. The terrain is flat during this stretch of highway.

Compared to Waze and various roadside radar "Your Speed" reminder signs, the speedometer usually overstates my speed by about 1 MPH.
 

Danal

electricmotorglider.com
Perhaps the cars' odometers are calibrated for a slightly smaller diameter tire? Maybe they forgot to fix it when they changed to the Michelin Primacys?

Yeah, I was wondering that. I tried to calculate the actual diameter change to produce 0.8% and I didn't post the numbers because I didn't believe them. It was 2AM, so I thought I'd try again in the morning. That's now. As soon as I wake up fully...
 

Andyw2100

Well-Known Member
Oct 22, 2014
6,542
2,443
Ithaca, NY
Perhaps the cars' odometers are calibrated for a slightly smaller diameter tire? Maybe they forgot to fix it when they changed to the Michelin Primacys?

I don't know how the odometers work, but something along these lines sounds plausible. The question though, then would be does the car have a different setting to indicate which of the Tesla approved tires it is currently using at any given time? If not, either all the Tesla approved tires would have to be exactly the same diameter or the odometer would intentionally be inaccurate by design with all but one tire.

Also, for what it's worth, I'm sure all of us reporting discrepancies aren't using the same tires. I have the Tesla winter wheel package, which includes the Pirelli Sottozero II tires.
 

Cottonwood

Roadster#433, Model S#S37
Feb 27, 2009
5,089
181
Colorado
Here are more data, Supercharger to Supercharger:

RouteSupercharge.InfoP85D
Gallup-Holbrook88.390.0
Holbrook-Flagstaff93.294.8
Cordes-Gila Bend125129.8
Yuma-El Centro57.258.5

[

Because the Cordes-Gila Bend was so much more, I looked at the route in Supercharge.Info and it was different and shorter than the on-board nav took me.

Yuma-El Centro looked a little off as well. I checked the Supercharge.Info, and it's location for El Centro was in the center of the mall. The actual Supercharger location is on the south side if the mall, accounting for some of the difference.

It seems that my P85D is reporting a percent or two higher.
 

Andyw2100

Well-Known Member
Oct 22, 2014
6,542
2,443
Ithaca, NY
Odometers measure wheel revolutions, so any change in tire size will affect the odometer reading, plus or minus.

Manufacturers have to set the odometer to a single, expected value - a center point tire size if you will - and are allowed a small variance, something like 1%, to account for different tires offered.

Another interesting fact is that as your tires wear down their diameter decreases which increases revolutions per mile, thus causing your odometer to read higher over time. The difference between new tires with full tread and worn tires down to their tread bar can be over 1%.
 

Andyw2100

Well-Known Member
Oct 22, 2014
6,542
2,443
Ithaca, NY
Odometers measure wheel revolutions, so any change in tire size will affect the odometer reading, plus or minus.

Manufacturers have to set the odometer to a single, expected value - a center point tire size if you will - and are allowed a small variance, something like 1%, to account for different tires offered.

Another interesting fact is that as your tires wear down their diameter decreases which increases revolutions per mile, thus causing your odometer to read higher over time. The difference between new tires with full tread and worn tires down to their tread bar can be over 1%.


This may all be true.

But that doesn't explain why people who have owned the Model S before are seeing an issue now when they didn't have one before. For example:


I noticed this on my very first trip with the P85D from NJ->NC after taking delivery. The trip meter showed about 6 extra miles vs what I expected from a dozen previous trips on the exact same route.

I think Tesla is probably just using a bad calculation somewhere.
 

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