On the Accuracy of Odometers

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All instruments have measurement error, independent of a human misreading their output. No yard stick is exactly a yard, no reasonably priced bathroom scale measures to the quarter pound, no chem lab balance is accurate to the microgram. Similarly for an odometer, which measures distance traveled.

Correct me if I'm wrong, but the United States has no federal or state regulation about speedometer or odometer accuracy; of course it is illegal to shift the odometer without posting a notice of having done so--even if the original odometer was reading wildly outside the design tolerance of the manufacturer. (Here are the federal regs.)

Tampering with automobile odometers is an extraordinarily costly problem. A while back the NHTSA studied 10,000 randomly selected automobiles to figure out how frequently used autos have their odometers rolled back.

NHTSA's study was requested by Congress and examined the title transfers of 10,000 vehicles and its own database of known odometer fraud. The researchers calculated that 3.47 percent of vehicles less than 11 years old have had their odometers rolled back, or about 452,000 vehicles sold each year.
From the full report:
The increased cost consumers pay to purchase passenger vehicles with odometer rollback of $1,056 million per year makes odometer fraud one of the top crimes against property in the United States. By comparison, the Federal Bureau of Investigations estimated that in the year 2000, auto theft resulted in direct losses of $2,900 million, arson $760 million, burglary $3,000 million, and shoplifting $200 million.

Even if you're buying a used car from a reputable person or dealer, there is still a very good chance that the odometer meter is wrong, even if it has not been tampered with. But the question when dealing with either an honest man or a crook is not "is the odometer wrong?", the question is "how wrong is the odometer?"

Even non-tampered odometers may wrong by a large amount, as tolerance levels for manufacturers differ; a consumer should know how this error tolerance effects their valuation of the car.

According to one calibrator merchant:

The speedometers and odometer on.... modern cars, are calibrated from the factory with a plus 1-2 percent error. This means that actual speed or recorded mileage is actually lower than that indicated on the speedometer and odometer.

Some organizations, when testing out cars, will examine speedometer/odometer error. Here are 5 foreign models tested in 2001:

Subaru Impreza WRX 3.2%
Ford Focus 2.1%
Chrysler PT Cruiser 1.07%
Toyota Condor 2400 1.54%
Volvo V70 T5 0.14%

One man claims the Porsche told him that 10% over (for a speedometer and apparently odometer) was with design tolderance. Another has a 2% overage.

Hence, if you're buying a car with 50,000 miles on it, the actual mileage can legitimately be 1,000 miles or more less than the odometer reads. Perhaps it's sellers, not buyers, who should be most concerned about this.

If this has amused you, see this longish treatment of mechanical and digital odometers.

Also note that the Iron Butt Association brings together those who motorbike long distances in short times--say 10,000 in ten days.

Their stringent rules require that applicants know their odometer error. One milestone has the following requirement:

WARNING: Unless your speedometer has been calibrated, do NOT depend on your own odometer readings for official readings! Most Japanese motorcycles register five to ten percent more kilometers than actually traveled. Over the course of a 24 hour period, this error can be quite severe - as much as 200 kilometers. IN ALL CASES, mileage will be verified with either paper or computer maps of the country you live in.

This man notes that race courses measured by auto odometers will be too short, yielding a who bunch of angry runners who really hadn't made personal bests...!

29 Comments

The Odometer of my new 2004 Chevy Malibu registers approximately 3.5% more miles than accually driven. Over a 200 mile stretch on Interstate 35 (using the mile markers for reference) the odometer indicated I drove almost 207 miles.

Because some Chevy/GM Tech Rep has stated "a +/- 4% error factor is acceptable, I have been told by the GM Customer Service people that I will have to live with situation.

Curious if any other GM/Chevy owners have experienced a similar situation.

Thanks, Wayne B., San Antonio, TX

My Audi TT odometer is off by an unfavorable 2.6% with sample data taken over 1,600 miles using GPS and mile markers. Over the life of the vehicle, I calculate that this error will cost owners $1,233/vehicle. I called Audi customer service about this issue and they informed me that odometers can vary in accuracy and that 2.6% is within manufacturing specifications (but they wouldn't tell me the actual tolerances)! I then sampled a friends Audi TT over about 300 miles and concluded that the odometer was off by 2.5%. Funny how a German company, known for engineering excellence, can be off by such a consistent amount. No wonder fuel efficiencies are so high!

I have a Audi A4 1.9tdi, it seems to be out between 8 and 10%, unfortunately I didn't have the functionality to test it against a GPS, but Audi did a few comparisons and found first found the problem when comparing it to a Volkwagen and the denied a problem when they compared it to an other A4. Thus all the A4 units are out with this much!

I have an '03 Acura TL. My father taught me as a young driver to check the accuracy of the spedometer and odometer using the 1-minute, 60MPH, mile marker formula. This car consistently adds .02 to every 5 miles travelled. I have also compared it with 3 different cars that were able to follow the same route directly behind with synchronized trip-odometers -- each time there was a significant difference. The dealer claims that they have road tested it against other '03 TLs and found no discrepancy (are they all off?, is it a plot???). I have asked them repeatedly to test it against a different make for at least a ten mile highway trip. No luck. Also, Acura customer service says it's an acceptable discrepancy. Since this is a lease, we are going to end up paying in the end for miles we didn't travel. Does anyone know how I can have the accuracy officially documented so I don't end up paying these theives extra money?

This conversation is ridiculous. If your speedometer is out by 10%, there is a calibration issue. If it is out by 1%, there is little that can be done because it will be affected by tire pressure as much as anything, and that itself changes with ambient air pressure. Since even the new tire pressure monitoring systems are only accurate to about 10%, complaining about 1-2% error really is splitting hairs.

I recently purchased a new 2005 Malibu LS. Using a Garmin GPS, I have determined that the odometer (and speedometer) readout high by 3.3%.

I complained to my dealer and was also told that as long as the error did not exceed 4%, the Chevrolet considered the 3.3% acceptable. However, I have calculated that when the new 10/32" tread depth on the tires wears down to the minimum 2/32", that will cause an additional odometer error of 2.0% so the total odometer (and speedometer) error then will be 5.3%.

My 2005 Chevy Cobalt has an odometer error of 4.5%. If I drive 200 miles, it registers 209 miles. Chevy assures me that this is normal and there is nothing that they can do about it.

Sounds like the manufactures are sending vehicles out with a plus milage ticker. This may be to shorten the 3 year or 36000 mile warrantee. Think about it 5% error used throught the 36000mile is 34200 actual miles driven.

Large European automobile companies may be hedging their odometer measurments based upon a "publicly denied rumor". Knowledgeable pundits have for years been aware of the intention by a triumverate of multinational corporations to secretly reduce the length of the mile standard. This would cause all new mile makers to be slightly shortened as they are installed throughout the world. Ultimately, as the perceived "exact mile" begins to shorten everywhere, all large coporations would benefit: cars would seem to run faster, tires would seem to last longer, races would be completed more quickly, which allows the viewing public to return to their work at an earlier hour.

No, my firend, do not concern yourself with the inaccuracies of the measuring machinery, but rather with the standard to which they measure!

4% x a million cars or so a year = a hell of a lot of warranty miles!

Buying next-larger tire size (most cars will handle one-size jump with same rim size) will more than adjust for odometer error on high side, and give you better tire wear, and more miles on your lease. Talking about odometers, I got my old 1995 200k+ miles car back from a tune-up a year ago, with 90k LESS miles on the odometer. I didn't particularly know the garage and knew no mechanic there; has any-one else had this (problem?). I didn't raise any questions. Can a major tune-up on a car mess up the odometer by accident?

My '05 Malibu is registering 10.4 miles for a highway mile marker distance of 10 miles. It is really interesting that while Chevrolet says 4% error is exceptable I'm not seeing any complaints here about undercalculating the odometer. I'm not usually one to buy into a conspiracy theory, but a 4% savings on warranties represents a significant cost savings to GM. Something about this stinks.

Get a life. Find something important to worry about. Speedometers always read higher, never lower in the USA. The lawyers would have a field day taking money in accident cases, money which comes from the consumers (you), anyway you slice it. Warranty isn't free, you pay for it when you buy the product (what are you thinking? Plots? conspiracies?). The manufacturer has to keep the selling cost as low as possible in order to sell more cars against competing makes. Remember when warraties were 1 year? What if you could buy a car with no warranty? It would only have "Voluntary recalls". They could cut $2k off the price of a $25K car. Contrary to thoughts expressed here, few warranty repairs acually fall just outside the warraty period, so the +5% us error isn't reallly a big deal. DUI, not paying attention, no seat belt use, etc... are big deals...

my 2003 chev avalanche odometer sometimes stops operating completly or it will drop down to indicate speed of 30,40,ect.or it will jump up to 100,110,or peg out all the while i maintain a steady rpm or gas pedal control it even does it when the cruise control is set. eradict odometer? anyone else having this problem? is there a recall for this? any help is appreciated

my 2003 chev avalanche odometer sometimes stops operating completly or it will drop down to indicate speed of 30,40,ect.or it will jump up to 100,110,or peg out all the while i maintain a steady rpm or gas pedal control it even does it when the cruise control is set. eradict odometer? anyone else having this problem? is there a recall for this? any help is appreciated

My 2006 Honda Pilot odometer registers 3% high on trips measured against highway mile markers. The Honda dealer verified this in a test drive and says this is well within the 5% manufacturer's factory tolerance. We keep cars for 7-8 years and this will affect the resale value as well as the warrantee period/coverage mentioned above.

This might seem like a stupid question. Do odometers work accurately if the wheels of the car are changed to larger ones say 2 inches bigger in diameter? The revoultions of the tyres would be the same but more ground is covered?

I recently upgraded from 235/75-15 tires to 31x10.5-15's on the same rim. The new tires are 2-3" taller and the speedometer error was -5mph and the odometer was -6/10 every 10 miles (marked Odometer test area). I reflashed the PCM with the new RPM/Speed to correct the transmission shift points and had the Ford dealer reflash the ABS Module with the corrct Revolutions per Mile and the speedo is dead on and so is the odometer.

My new Toyota Corolla Verso (2006)has been registered as 10-15% slow against radar-measured speed signs, and against other traffic, and generally felt slow. When I took it to the dealer for the 15000 km checkup, I asked them to check (European Motors Company in Stockholm, Sweden). They said that mechanically measured, the speedometer showed 50km/hr when it was only going 40 (20% difference). Then they measured it (conveniently) on their computers and found that when it was going 50 it measured at 46 km/hr. This was "only" 8% off and deemed within acceptable limits (this is still pending and I will run a campaign if they do not do anything about it). What this means is that if I am running almost 10% less than it shows, the car will be showing 200,000 km when it has only gone 180,000, seriously deteriorating resell value. Plus, as another wrote here, it puts it out of guarantee 10% sooner. Finally, the wonderful gas milage I thought I was getting must be adjusted up almost 10%. If it is really measuring 20% off in the middle speeds, then it is even worse. How can Toyota claim that 8% is an acceptable error? In addition, time calculations for long trips are off, since (unless I try to allow for a major percentage increase in speed and chance a ticket). But above all, I am essentially being blown a big chunck of resell value.

My problem is speeding tickets...I got one going 40 on a 25mph zone; I don't think I was going 40, my speedometer reading was definitely under 40, but the officer said I was going that speed and gave me a ticket. I feel there could be a problem with his radar gun or my speedometer or maybe I was going 40.
I know I was wrong for going over the limit even though I thought that zone was a 35 or 40mph zone
and to go 25 you need to keep your foot on the brakes. It is a speed trap!
Any comments???

John,

If your speedometer is off, you're still liable for speeding. However, if the radar gun is off, then in order to get this reversed, you'll have to contest the ticket, which is incredibly difficult. If you do contest, you must demand to see the officer's training records, the radar gun's calibration and maintenance records, etc.

See more details at the National Motorists Association website.

sdretsaB daS

i have a 2006 nissan altima with 43000. only drive the car on small trips to work or grocery.been a few times within a 100 mile distance. there is no way this car should have this many miles on it. ihave taken it to the dealer four times and they say nothing is wrong. has anyone else had this trouble?

My 2005 Tahoe odometer is off by 3.26% - the mileage shown on my odometer is 3.26% higher than the actual mileage.

I have a 1988 Honda Coupe, Lxi, my front tires were bad because of a bad tie rod end. I tried to have the front end alig. and but it kept pulling to the right, so I wanted to get some tires to last the summer, so I purchased to real good 18570x14 instead of the 19560x14. So I looked up the difference in size to see if it would change much. Well this opened my eyes, I had gone thur some of those speed reduce ares and saw my speed as 58 mph when my speedometershowed 60 mph. So I checked it with a GPS, it in deed was off by about 1.5 to 2 mph at 60 mph. The tires I changed to were 4.2% slower than the stock ones, So now my speedometer reads just about right. But I loss about 1.5 mpg in the dead, the in realty I was not getting that, anyway....

Good info here, thanks guys!

2005 Audi A4 Cabriolet 3.0L, stock wheels and tires, inflated to recommended pressure. Speedometer consistently displays 5 mph faster that GPS at 60 mph, i.e. over 8% faster. Tested GPS in Murano and Acura at same speed and GPS was accurate within +- 1 mph with both test vehicles’ speedometer. Asked Audi Dealer in Syracuse NY about discrepancy and was told that all Audis are calibrated to show speed faster by 5 mph, purportedly for safety reasons. I assume the speedometer and odometer are linked. The yet to be answered question from Audi is: Will my 50,000 mile warranty be extended to 54,000 miles?

2005 Land Rover Freelander speedometer reads 8-10% high (GPS & radar). Odometer reads 2.5% high (GPS & mile markers). Rover customer service says that is within tolerances. Additionally, they say that GPS, radar and mile marker tracking are not acceptable proof of this discrepancy. My only issue was the $1800s of engine work the car needed at 51k miles. Land Rover customer service was unwilling to help. Warranty should have covered it. Honda settled a class action suit and added 5% to many 2002-2007 car warranties. My local (Santa Fe, NM) Nissan dealer covered an issue with my old Pathfinder about 3k miles after the warranty was over. NISSAN = good customer service. HONDA = forced customer service. LAND ROVER = no customer service.

I think you could safely assume that if you tested a large lot of cars out on the road, you would find an average discrepancy of about 5% or so. That being said, you're not loosing resale value, or warranty. Why? Resale value is for the most part a comparison of a vehicle's condition compared to others of similar age. Resale value is not based solely on the odometer reading, and anyone who buys a car based solely on the odometer reading is a fool. For those who think they're getting messed around on their warranty, I suggest you read your owners manual. All the new vehicles I've had in the last 20 or so years have disclosed odometer and speedometer discrepancy in the owners manual. Using your brain would tell you that this discrepancy must also apply to the warranty. That's why any reputable automaker/dealer will usually warranty something that is out of warranty miles by only 5-10%.

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This page contains a single entry by Kevin published on June 18, 2004 3:33 PM.

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