Someone asked me to pass along any info I gathered on this, so here goes:

To recap, I have confirmed through GPS tracking, police radar and side-by-side tracking with another vehicle that my speedometer reads 3mph higher than my actual speed. IOW, when my speedometer shows 30mph, I'm actually going only 27; when it shows 60mph, I'm actually doing only 57, etc.

It occurred to me that my odometer must also be reading too high, meaning it is racking up too many miles. That's a factor not only for warranty purposes, but also because I have a lease with 15,000 miles per year and if I exceed that I have to pay Lexus 20¢ per mile. At 45,000 miles, that will amount to about 2,250 extra miles, or about $450.

I wrote Lexus a nice letter outlining this and asking that they cut me some slack if I exceeded my mileage limitation. They called me and told me the speedo and odo use entirely separate inputs, so the fact the speedo was off didn't mean the odo is. (They couldn't comment when I asked if that therefore meant they could BOTH be wrong. )

So today I sat down with my dealer's Shop Manager and we studied wiring diagrams and system flow charts for an hour. What we concluded is that:

1. In addition to wheel sensors, the speedo does indeed use some additional info sources, like wheel spin sensors, that the odo ignores. (After all, if the wheels are spinning the speedo needle shows it, while the odo doesn't, since the car isn't really moving.)
2. The odo relies primarily on the wheel sensors to record forward movement, as expected.

The interesting point, though, is this: The signals from both the speedometer pickups and the odometer pickups are run through something called a "Certification ECU", a computerized control unit that appears to compare and confirm (certify) the values. After taking into account the signals that don't apply to the odo, the values must essentially match or the system will register an error code.

What that says to me is that if the speedo is off, the odo is off.

It is well-known that Acura lost a class action suit for this very thing a couple years ago, and they ended up extending warranties and mileage on leases. I'm not trying to stir up a lawsuit, but I have again written Lexus asking that they consider this discrepancy if my mileage exceeds 45,000 at lease end.

Take it for what it's worth.

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Gee, I wonder why Lexus changed their warranty policy from four years/48k miles to four years/50k miles.

It seems like owners break even, but leasees don't.

Sorry.

 

I did a similar test with my GPS and found exactly the same results - the GPS reads 3 MPH slower than the Lexus speedometer. I am assuming that the GPS is correct. It's a Garmin Nuvi 350. What I didn't do was use the mileage indicator on the GPS to compare with the odometer reading. Of course, when you go very slowly, there is not the 3 MPH difference - for example when you are stopped, the GPS doesn't read -3MPH. It is strange that the error is constant with speed (I could measure it best using cruise control so the car would have a steady speed and the GPS would not have a delay in recording the changing speed.) This was true from about 35 MPH, the slowest I set cruise control, to about 80 MPH. It also should mean that the true MPG readings should be lower than the display shows.

 

Yes, you're correct - the mpg readout is biased by about 5% ... assuming the odometer is off the same amount as the speedo.

And I also agree it's odd that the 3mph differential holds at all speeds, rather than being a percentage error. My assumption here is that it is lost at the beginning of the speedo travel and never recovered.

BTW, I've tested mine down to 20mph. At that speed, I'm doing 17.

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I didn't get into what u were talking about very deeply, but quickly reviewing what is told, I understood, that you think, that ODO shows more KM because it shows not correct speed? Did I get it right?

If it is about this, I can tell you one thing > If everything on the car is stock (tire sizes specialy) then car KNOWS your exact speed, but it is displaying your speed on speedometer with some more speed, just for some lowsuit not to get involed.

Don't believe me? Try this (just I don't remember if there is an Average Speed display on center in LS, but think there is):

1. Go to some highway > for keeping constant speed without disturbance
2. Set cruise control to be without radar (that speed won't change because of any other cars) to a constant speed lets say 100km/h
3. Make sure u are going speed you set and on speedometer display choose Average Speed to be shown.
4. Reset it, by presing "reset" (keep in mind that you are still cruising at the same 100km/h speed, and speed is not changed)
5. It will take about 5seconds, to show average speed, that will be all the time at constant 100km/h.
6. If you have your garmin on the windshield, you will get EXACTLY the same speed on "Avarage Speed" display as your Garmin GPS speed.

 

That may be, but the issue is the odometer reading. I'm assuming if the speedometer is showing too fast, then the odometer is, too, since they're operated by the same system.

By the way, what you say isn't true of all cars. My wife's Acura speedometer is spot-on with GPS and with police radar. Exactly. When her car says 30mph, it is going exactly 30mph. As I noted earlier, Acura got sued for incorrect speedometer/odometer readouts, and they've made theirs very accurate!

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Odometer shows CORRECT distance. (can try doing the same by reseting trip A ar B and compare distance with GPS) Speed that is shown to you, is made purpusly a bit bigger for indivual car manufacter purpuses.

p.s. most of Chrysler cars olso show exact speed, it is how the company desided to do.

 

Again, Andriuss, you may be correct. But it is up to Lexus to convince me.

In the case of Acura, the speedometer and odometer were equally incorrect, which is why they extended the warranty mileage and the lease mileage. I suspect it is the same with Lexus, since it is difficult to make the speedometer and odometer display different readings when they use the same system to collect their data.

I'll see what Lexus says.

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Nothing has ever been proven to show Toyota/Lexus odometers are off more than the lawful amount. Readings car vary based on a multitude of factors.

http://www.hondaodometerclassaction.com/

http://www.autoblog.com/2007/02/19/o...-million-cars/

Odo Uh-Oh: Honda extending warranties on 6 million cars

by John Neff (RSS feed) on Feb 19th 2007 at 12:25PM
Honda has decided to settle a class-action lawsuit that alleges its odometers were racking up miles too fast. The automaker says odometers on some 6 million Hondas affected by the suit were accurate to within 3.75% on the high side. The NHTSA doesn't regulate odometer accuracy, and the only industry standard is a voluntary one set by the Society of Automotive Engineers that says odos should be within +/-4%. While the car's affected by the suit fall within that range, Honda recognized that its customers expected their odometers "would be based on zero," and they weren't.

The settlement will lengthen the warranty mileage of affected vehicles by 5% and Honda will pay lease-mileage penalties incurred by owners, which is expected to cost the automaker around $6 million. If you own a 2002 to 2006 Honda or Acura bought between April 12, 2002 and November 7, 2006, then you're eligible for the benefits of the settlement.

The lawsuit also prompted lawyers to test the odometer accuracy of other vehicles. It was found that on average domestic vehicles were nearly perfect in their odo accuracy, while Toyotas actually racked up fewer miles on the clock than they did in reality. Nissans, however, didn't fare as well, and a new class-action suit has been filed on behalf of Altima owners who say their odometers are counting the miles 2.5% to 3% faster than they should.

[Source: USA Today]

Good info on NSXPrime

 

^ Good info ^ Thanks.

It is true that speedometers will vary some, and it's not a violation of any law or anything if they do. As pointed out, even the amount of wear on your tires will affect the reading s to some extent, so mfr's can't always guarantee absolute accuracy.

My appeal to Lexus is based on the fact they will charge me for excess mileage when my lease ends, but I've proven to my satisfaction that the speedometer is wrong by enough to cost me close to $500 of undeserved charges. I just want them to take that into consideration on my lease.

I've told them I'm willing to let them test my car any way they want to verify the error, or otherwise show me that it's not wrong. We've been very polite to each other, but I feel their first answer to me wasn't accurate and I'm pushing it a little further.

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Just to play devil's advocate, would you offer to pay Lexus $450 at the end of your lease if it was determined that the vehicle actually had 2,250 miles MORE than recorded?

Not that I'm discounting your concern or having a dig - just pointing out it might not be worth stressing over. You're talking a few percent on 45,000 miles - I'm confident most cars outside of police interceptors are off to some extent, don't sweat the small stuff!

 

Hey - recording miles is their responsibility, not mine. They designed, engineered and built the car. So if it somehow turned out the car didn't report enough miles, I'd not be inclined to pay them.

And I don't think it's "sweating the small stuff" to fork over $500 when I don't feel I owe it. If $500 is small stuff to you ... how about I PM you my Paypal account ID and you slip me the money?

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I suppose what I meant is, why are you worrying about this now? IF you drive 47,200 miles on your lease, why not take all of the information you have (namely the police certification you obtained, Lexus most certainly won't care about your GPS reading and the wiring diagram) and present it to Lexus at that time. I'm quite certain they would be unconcerned with the $450 discrepancy at that time, especially if you're getting another Lexus.

You've clearly spent quite some time researching this - I guess I don't

 

Well, I'm thinking about it now because if I continue racking up miles like I have so far I'll exceed my 45,000 mile lease allocation by next year when the lease is up. I had suspected for a long time that the speedo (and probably odo) were "off", so I checked the speedometer a few months ago. When it did show to be incorrect, I wrote Lexus the first letter.

They called me a few weeks later to discuss it, and basically told me I was wrong. So I let it drop for a month or two, then finally got a chance to talk to someone at the dealership just this past Friday.

As far as trading for another Lexus, I may or may not. And even if I did, they'd probably just bury the mileage charge in the price of the replacement car anyway.

But I guess I'm not like you. When something isn't right, it bothers me - especially when it costs me money because it's not right. If I felt I really owed the mileage charge I'd pay it. But if I feel it's bogus, I'll fight it.

The reason for taking it up with Lexus now is to get on record with them early in the game ... not wait until the lease is up and try to fight it then.

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If only you knew me, Mike! I've made dealers disassemble vehicles to ensure perfect alignment of exterior trim. I replaced the entire center console because of a tiny nick hardly noticeable to most "normal" people. As we speak, my LS460 is at the Lexus collision center getting cosmetic touch-ups. Oh believe me, everything bothers me!

In hindsight, I suppose I can sympathize.

Good luck with the battle.