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-   -   Does the odometer really reflect engine wear and tear? (https://www.team-bhp.com/forum/technical-stuff/109058-does-odometer-really-reflect-engine-wear-tear.html)

When we look to purchase used cars, or even consider them as a spectator sport, one of the first thing we look for is the odometer reading. The lower the number the better it is, since low number is a reflection of lower amount engine wear and tear as the car has done lesser miles. Basic stuff isn't it? For example, a 07 Swift with 20000Kms of city drives commands a better perception than 09 Swift with 50000Kms of city-highway kms.

On a different note, for our own vehicles, we mostly look at the odo for choosing service dates. Even though most OEMs recommend a odometer milestone or a 6 month interval whichever is earlier, many of us stick to odo milestones (10k, 15k, 20k etc).

I was thinking of a different angle to this debate, somewhat fueled by BHPian Dhanush's comment a few days back on a different thread.

What he says is true. A corollary to this point is that, in urban traffic, when the car is idling for ages, all moving components in the engine are chugging away in glory and the odo does not serve as a record for that.

Let us consider an imaginary Swift which is serving in place like Bombay or Bangalore. The car would have idled and crawled in dead slow traffic for about one or more hours daily. So even if the car has traveled low number of kilometers, there are hidden miles which are not recorded at all, as shown below.

It is assumed that one hour of idle takes up 1 liter of fuel. If city FE is 14, then in one hour of idle or dead slow traffic, 14Kms of ticks is not reflected on the odo. Multiply this by 5 ( one week) and 50 (one year), it amounts to 3500Kms.

So for a 2 -4 year old car, about 7000-20000 Kms worth of engine run is not reflected on the odo, depending on the amount of time the car has spend in crawling traffic.

What this means is that if we are in the market to look for used cars, we need to add a few thousand kilometers to the odo and make an estimate of the condition of the engine.

This is also perhaps why, we need to ensure regular service of our cars which are undergoing torture in city crawling conditions, using date milestones. We might have traveled less kilometers within a city, however the engine has revved much more, engine components has gone through many more cycles of operation and engine oil has served for a larger time.

The distance you travel in your vehicle does tell you how often your tyres should be changed but the date of manufacture and the amount of tread wear are equally important. The same goes for the rest of the vehicle. The use of the AC, staying parked for months together, climbing uphill, revving the engine hard, and lugging the engine aren't something the odometer is going to tell you. In the U.S., if you sell a vehicle with a 5-digit odometer and you know you've run more than 99,999 km/mi then you put down he odometer reading as-is and check a box that says "mileage exceeds the mechanical limits of the odometer", with mileage not referring to the distance covered and not FE as discussed here.

I visit the service center at least every alternate month despite having covered less than 1,000km simply because the vehicle is used frequently for very short trips and the essential parts of the vehicle can be checked for any signs of failure.

Pretty good one Dot. The statistics and analysis is Dot on the issue and one of the main aspects of doing the car valuation.

You will observe that owing to this, the car valuation also differs.
A car in Mumbai/Pune and a car in lets say a B-level town like Nashik/Nagpur both having run 10000km in a year would command different valuations and the B-level city car would probably fetch more price for various reasons:
1. as pointed by you the idling, running in Mumbai/Pune would be more actually
2. the weather effect on the car
3. the upkeep of the car, in Mumbai/Pune one can hardly keep a car in its natural shape and look whereas in B-level town you will find many cars kept in better shape.

So, all these factors do contribute to the ageing of the car in respective places and the price valuation is done as per that.

Nice thread! In fact one of the reasons why sellers advertise city miles or highway miles is to give an indication of the daily usage. of course there is no real way to cross check this claim, but having an idea of the sellers driving pattern would be helpful.

In addition to additional engine wear and tear in city driving, there is also the fact of higher load on the cooling system.

Interestingly, the Xylo has an AC odometer, which keeps ticking even while the vehicle is stationary (at 1km/minute).

The odometer gives an indication of usage but not the whole story. It is only when you combine the odometer with age and the base location that some idea of usage emerges. Add to this a test drive and a visit to the mechanic/workshop for thorough evaluation.

In fact very low milage in a relatively old car is as bad as a very high milage car. In this case the car may be standing still for weeks and taken out occasionally, thus accumulating gunk in the engine. As the car travels very less the maintenance may also be lackadaisical.

An extremely valid point brought up Dot!

When our vehicles reach the scheduled service point, we convince ourselves that a few kms here and there wouldn't really affect anything; many even postpone just because the running ain't that much.

But with the kind of traffic jams that we almost regularly face in almost every part of the country, the engine invariably runs much more than what the odometer reveals.

And when stalling, the engine isn't at its optimum either because lack of air flow.

All said and done, I think even the 1k rpm the engine runs at during idling must be contributing significantly to the engine life.

Point to note : follow the time interval specified in the service schedule too; not just the kms run.

PS : I hope no manufacturer is following this thread; else, all warrantys will see reduced mileage limits! :D

absolutely.

An extension of this is that a 1,00,000km 4 year old well maintained car is in fact a better buy than ,say,a 10 year old car with only 25000kms on clock.

The engine can be evaulated from the purr ; the closer it is to stock,the better

Exactly dot, this is exactly why I insist, a 1L highway driven NEWER and well maintained car is ANYTIME better than a 50000 city driven, OLDER car.

I can vouch for this from my personal experience.

Hi,
Are we talking of the car as a whole, or just the engine?

Regards
Sutripta

I was trying to scan the net on this subject and most of the hits were related to heavy vehicles like excavators, trucks etc. This is expected as many of these construction behemoths spend a lot of time idling, which contributes to engine wear. It seems to be a known issue for these type of vehicles.

For cars, as pointed by k_nitin_r and parsh, many of the activities are hard to distinguish and taken for granted.

Once we were playing around with an OBD tool and found that during idle, whenever the AC compressor would switch on, the load level would go to 100%. This is not the case when the car moves.

BTW, I didnt understand the AC odometer's function. Can you elaborate or point out to a thread which contains a discussion on this aspect.

Thats exactly the point why I started this thread to have a discussion around it. Question is, whatever we are discussing on the time milestone for engine oil change is really true or an owners' paranoia.

I believe, this can be nullified by shorter engine oil change. After all modern engines are designed to run for hundred of thousand miles.

Agreed. Somedays back a friend asked me if it was worth looking at a Fiesta (Classic) which is 2-3 years old and has run over 1 lakh kms. The original owner was traveling between Bombay and Daman every alternate day, that why it had added miles to the odometer. My assessment was if the service has been done on time, the car should be a good buy.

The engine mostly.

A fair amount of discussion is available here

When it comes to causing you grief, there's far more to a car than just the engine!

Regards
Sutripta

I am sorry sir, I didnt understand which part of a car causes grief.

dot, I guess Sutripta sir is pointing towards the other mechanical parts which wear off only while the odo ticks along. Like the suspension, the GB et al.

In any case, even these parts face much lesser wear and tear, if driven on a highway, than in city. Hence my comment.

So, basically here's what you all are saying? A car thats done highway runs (and serviced regularly) is better than the one that's driven in the city? If so, what about other aspects like suspension, the metal body etc. Would'nt they also show wear and tear of a car that's run so much?

Dotty, I agree on the point though that when looking for a used car market, we need to take into consideration the idle time, hence adding a few thousand kms to the count shown.

P.S: Just another look to the entire argument - What if the Odo of the car itself is tampered?