For those never exposed to the subject, OTR diesel trucks run a million miles regularly. I had one 1979 International cabover, 800 cu in, 400 hp, Big Cam Cummins with over a million with 1 inframe overhaul. Large OTR trucking companies trade in their trucks at around 450,000 miles and out they go to small time operators, lots of rock bucket towers, for another 500,000 without a wrench on the engine proper. Most run oil quality tests and don't change oil till the test fails a certain criteria.....for you 3000 mile oil change folks.
Even if you take a very conservative 50 mph and that doesn't include the OTR trucker leaving his rig running all night at the truck stop in cold weather, you are looking at 500,000 miles/50 mph = 10,000 hours without overhaul ready for another 10,000 from a small time operator with maybe 1 inframe overhaul.
How many of you guys are going to run your tractor 10,000 hours? If you are a BTO (big time operator) you probably will but you will also have a big shop, lots of helpers and all the resources to put it back in service for another 10,000 and you can write all that off your income taxes.
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You know, they put idiot lights on dashboards of most consumer type vehicles so that the owners "can worry about something else" instead of getting hung up on whether the needle is at 12 o'clock or 12:30 o'clock!!!!!!!!!! (yes and they are cheaper to produce than gauges)