Every new car sold must have an odometer, and many (if not all) US states have strict regulations against tampering with them or misreporting their displayed values.
But an odometer is not the best indication of drivetrain wear; a car that has been driven for 30,000 miles may have experienced much more wear on pistons, valves, and crank- and camshafts than one showing twice as many miles. This is why you'll see used car ads that say things like "100,000 miles, all freeway!"
So in addition to counting miles driven, how about total engine revolutions? A car that's been driven at cruising speeds on highways (i.e., for long periods at low RPMs) will show lower total revs than one that's been run near redline for much of its life, and should have correspondingly less wear and tear on key components.-- HP LoveJet, Jul 23 2002 Back-seat driver auto-patronising device Back-seat_20driver_...atronising_20device [hippo, Mar 20 2009] Such rotational counters exist on many types of equipment, even if passenger cars are not normally among them. IMHO, the bigger problem with such a device is that it won't tell you whether the previous owner believed in changing the oil every 2500 miles or every 25,000. Little details like that are far more important to the longevity of the car than the number of times the engine has gone around.-- supercat, Jul 23 2002 thought this had to do with hellfire & damnation invoking priests-- po, Jul 23 2002 Most machines requiring routine maintenance that cannot rely on an odometer use an Hour Meter.-- Mr Burns, Jul 23 2002 this would also encourage people to drive slower- well, with less revs, to retain more resale value of their car. This would surely cause less emissions/noise pollution. Shame for people with small cars that have to rev the tits off them to make them move.-- timo, Jul 24 2002 //this would also encourage people to drive slower- well, with less revs, to retain more resale value of their car.//
When driving in any given gear, the number of revolutions per mile driven will be roughly constant (the number or revs per odometer mile will be exactly constant). If anything, someone who drives more slowly is likely to be in a lower gear than someone who drives faster; consequently they would record more engine revs per mile.-- supercat, Jul 25 2002 An hour meter, or engine clock, isn't an expensive item to install. But before automobile manufacturers are willing to spend the extra dollars to buy the parts and install them, they will have to be convinced that this will sell more cars or make them more money.
A revolution counter could also easily be installed, and would serve the same function as an hour meter. And it would meet the same economic objections.
Higher revs do not necessarily indicate higher wear, under normal driving circumstances, A car that is routinely driven at highway speeds of 60 mph (100 kph) for hours at a time will not have the amount of engine wear as a car that is driven only 5 miles daily- because the car that is used only for short trips never reaches optimum operating temperature. A ten-year-old car with 60,000 miles on the odometer (100,000 K) may have less life left than a 2 year-old car with the same mileage.
Two features that would help prolong engine life are an electric auxilliary oil pump- to pump oil into the journals before the engine is turned over- and an hour meter that disables the starting circuit at regular service intervals.
The first feature is an electric oil pump that is activated by the ignition key being switched on. Only when the oil pressure reaches an acceptable value is the starter enabled- thus the engine doesn't start without sufficient oil pressure.
The second feature, an hour meter activated by the ignition switch, disconnects the starter circuit when the hours of operation number reaches a certain value, such as 100 hours of operation. At this point, an override switch must be pressed each time the car is started in order to enable the engine to start, so the motorist is nagged into getting his oil changed.-- whlanteigne, Oct 14 2002 I like the nagging thing... most people will ignore the 'service light' that most modern cars have installed (I assume running either clever oil quality models from the operating characteristics, or some kind of oil quality meter). The trick is to allow the engine to realise the oil's been changed, and not require a mechanic to plug in the laptop to tell it it has, as there are (despite manufacturer's attempts to dissuade them) still a significant number of people that are happy to change their car's oil themselves.
The auxilliary oil pump thing is a good idea, even if it's way too expensive an option for most manufacturers to even consider fitting (£10 per car * 25,000 cars/year is an entire design team paid for).-- Skrewloose, Mar 20 2009 look they are available, you can order digital tachometers that rev count and many many many vehicles without speedometers have an "odometer" on the tachometer that reads something like "XXXXXXX hours at 2000 rpm" which is used for setting maintenance schedules (still recorded in "hours"). But as the annos have indicated a "number of cold starts" counter would be as effective as well as a "number of previous neglectful owners" counter. Manufacturers don't like to install devices that will make you feel bad about how you drive.-- WcW, Mar 20 2009 A tachograph or BSDAPD (link) output for the entire life of the car would answer most questions.-- hippo, Mar 20 2009 An engine "black box"? It's a good idea. Consider however the relative merits. If it wears out, we replace it right? If a regular maintenance schedule will keep the car in reasonable shape until it is obsolete then any more expensive regime is simply a waste of money. If an engine needs rebuilding then when it is disassembled we can find out what failed and try to rectify it but otherwise the information, the history, is essentially trivia, a curiosity. The pace of change makes close examination of the minutia of the past worthless. We move on, fix what broke and learn from our mistakes.-- WcW, Mar 20 2009 random, halfbakery