Speedometer Readings and their Reliability

[Z4MAD]

Dear Comrades,

I believe it is fair to say that most prospective purchasers of a motor car are inexorably drawn to those that have a low mileage. However, I am interested to learn of how much reliance one can place upon speedometer readings. For example, it may well be possible to adjust the readings on the odometer, should this be the case and the mileometer reading has been tampered with, would this be identifiable within the electronic memory/computer of the motor car?

With kind regards,

MAD

[Ed.Straker]

When I looked into this I found that the E89 has its mileage recorded in at least two non volatile locations and compares these at start-up.

Any significant discrepancy sets a visible tamper dot in the display which is not removable by mere mortals.

Anything can be altered if you try hard enough but this issue seems well beyond the level of the average dodgy dealer.

Public accessible MOT history by now on all E89s would alert you anyway.

[bigwinn]

Not sure what software the E89 runs on or has potential to defeat, however they are of the age of car that a KM blocker could be fitted by previous owner which would not show as a discrepancy (all locations for stored mileage would still agree and hence no difference)

But how you prove/check that is as Ed says a diligence check on MOT history mileage?

[mcbutler]

Not on newer cars (E89 included), the info is recorded in several locations including I believe the key. BMW drop the key into a gadget that reads your info, if your daft enough to use a main dealer that is!
I am pretty sure you can check this with carly as well

[Pondrew]

I was told by a BMW dealer that the mileage is stored on a tamper-proof, solid state "chip" within the electronics, which can be accessed by them. How true this is I don't know.

[Andrew Sheldon]

The main concern I have with low mileage cars is what kind of driving they have done to achieve a low mileage. Was it for instance a load of stop start driving at low speed which by its very nature is not good for the mechanics and wear of a vehicle. I sometimes see a high mileage vehicle that has probably racked them up on a motorway which at the end of the day is far easier on the vehicle, yet we are so frightened of high mileage cars.
And yes modern vehicles record the real mileage in more than one location on the computer to my understanding so its not like the good old bad old days where people used to back the clock using an electric drill...
That said I am sure there are still bad peeps out there with modern software that can alter a cars mileage, especially in the first three years before its 1st mot..

[Ed.Straker]

The main concern I have with low mileage cars is what kind of driving they have done to achieve a low mileage. Was it for instance a load of stop start driving at low speed which by its very nature is not good for the mechanics and wear of a vehicle. I sometimes see a high mileage vehicle that has probably racked them up on a motorway which at the end of the day is far easier on the vehicle, yet we are so frightened of high mileage cars.
And yes modern vehicles record the real mileage in more than one location on the computer to my understanding so its not like the good old bad old days where people used to back the clock using an electric drill...
That said I am sure there are still bad peeps out there with modern software that can alter a cars mileage, especially in the first three years before its 1st mot..

I think you are spot on.

Some of the reasons cited for the premature demise of the N20 cam chain system is it seems to appear most in cars who use the stop / start a lot and /or poor oil quality..which is usually partly BMW stupid oil change intervals and in part to owners refusing to get a service done..

I think we've all seen cars that have racked up mega miles and are running as sweet as a nut.

Even things like seat wear on bolsters is more likely people getting in and out all the time on short journeys rather than someone sat driving for several hours.

[Starman]

I find my speedometer is off by 5mph at almost all speeds on the low side. So the thing tells me Im doing 60 mhp when everything else tells me Im doing 55MPH. This would effect the mileage on my meter significantly... it says I have 36,000... it probably had more.

I just wondered if it has to do with the 19" stock BMW rims I have.

[tiglon]

I find my speedometer is off by 5mph at almost all speeds on the low side. So the thing tells me Im doing 60 mhp when everything else tells me Im doing 55MPH. This would effect the mileage on my meter significantly... it says I have 36,000... it probably had more.

I just wondered if it has to do with the 19" stock BMW rims I have.

Speedometers are always set to read a higher speed than you are actually travelling (some cars are an exception to this, I think those that only have digital speed displays), to give a margin of error. Usually about 10%. This won't effect your odometer reading.

[ronk]

The first three years the car will probably have dealership history to keep the warranty valid. I don’t think many will spend £40/50k on a brand new car and take it to the local garage?

I don’t think there are many “clocked “ three year old z4’s out there. Most of them will have main dealer history.

If buying a car, talk to the servicing dealer and look at receipts - they will also have the end of warranty report.

[Pondrew]

If buying a car, talk to the servicing dealer.

Good advice. If the car has a digital service history, any franchise dealer should give you the information (or any info available). I have done it many times before going to view a car. It is also useful to compare with what the seller is saying. The amount of cars advertised with "full service history" that have nothing of the kind is truly amazing.
I always call my local dealer, saying I live nearby and am looking to buy this car. Then give them the impression they will get the servicing work; they tend to be a lot more forthcoming then

[Pondrew]

(some cars are an exception to this, I think those that only have digital speed displays),

I had a Mazda6 with HUD where the HUD speed was about 6% different to the analogue speedo. That was annoying to say the least. Not as annoying as it changing the sat-nav language whenever it felt like it though

[tiglon]

(some cars are an exception to this, I think those that only have digital speed displays),

I had a Mazda6 with HUD where the HUD speed was about 6% different to the analogue speedo. That was annoying to say the least. Not as annoying as it changing the sat-nav language whenever it felt like it though

I imagine that a different language on the sat nav every now and then would make life interesting! Does anyone know if you can change it on the Z4?

[Silverstar]

Back in the day when I was in the trade, I knew some who had lease cars and to keep them within their mileage limits they would simply remove a fuse which would stop the odometer from turning together with maybe a couple of other things like the radio or sunroof etc. Not sure if it worked on BMWs but I have seen it done on other cars and far as I know it's not detectable since you aren't actually winding the mileage back.

With regards to the service history, I used to call up the dealers to confirm or get complete history on a car but sometimes the dealer would refuse to give any information citing data protection rubbish.

[Z4MAD]

Dear Comrades,

I have just noted from transposing myself into the the ethernet that there are numerous advertisements for 'Mileage Correction' and 'Speedometer Correction'. It would appear that most are mobile and operate remotely visiting customers cars to perform the procedure.

All very interesting don't you think? Also it is absolutely corrupt and quite disgraceful behaviour both by the performer of the deed and those wretched reprobates who pay them for their nefarious acts.

With kind regards,

MAD