( whys ) some of the


i was told the( oil )in a car so long as the oil is-not over heated lasts for over 40000 forty thousand miles and even more. what does happen and the reason ( why ) the filter and oil is changed is the oil gets ( contaminated ) by mainly cylinder wall leak down, and secondarly from internal wearing of engine parts


You’ve answered your own question. Change oil due to internal wear as well as brake down of the properties in the oil after being heated and cooled over several cycles of starting and running of the engine.


There are places within the engine where the oil is subjected to hundreds of degrees…places like in bearings, and cylinder walls, and pistons surfaces, etc.


What you say is true. But car owners do not have any simple way of knowing when their car’s oil is about to become ineffective, so they change the oil well before that possibility arrives. Does that answer your question?


if you take a sample of the oil in your car to an independent lab they can analyze how the oil is “holding up” to the age, breakdown, and viscosity.

so it is possible to have a considerable time between oil changes.

however; since an oil change costs about 20 to 30 bucks, and an oil analysis costs around 100 it is really better (and more cost effective) to just change your oil when it says to in the owners manual!


Actually, these guys will do an analysis for $20-30:


It’s worth doing an analysis occasionally to see what kind of contaminates are in your oil (tells you something about the condition of your engine). In may cases you will need to change your oil due to contamination long before it actually breaks down.


Modern oils in a modern car in good condition can easily go 40,000 miles … usually. There are times it will not work out all that well, especially if your driving conditions are hard on oil and the complex additives.

Oil is cheaper and easier than lab test and possible errors. Follow the recommendations in your owner’s manual.


To be clear, I wouldn’t use lab tests to extend oil change intervals, just as a diagnostic tool to keep an eye on the engine’s condition.


Oil will never lose its lubricating properties, its the detergents in the oil which break down. Look at your dipstick at 3,000 miles. If its black, then change the oil.



If you remove the oil and put it in a jug for five years it will become crystal clear. Gravity is the best filter. It could be used over again if some additives were included. They used to sell reclaimed oil. Remember when Quaker State label used to say made with virgin oil? Even new oil settles out if left on a shelf.


Oil needs changing for more than one reason. There’s particulate contamination, as you’ve described, as well as dilution and contamination of the oil by combustion gasse and byproducts blown past the piston rings. Www.carbibles.com has a good primer on oils.

You should change you roil per the manufacturer’s recommendation.

Yes, in the can it will last indefinitely…however the formulation “grades” of oil change over time as the technology develops, and engines are developed and tested using current oil formulations, so never use a can of oil that was produced prior to the year of manufacture of the vehicle.


I find it interesting that you posted about a new type of gasoline engine you want to prototype under the heading: “to the thinkers , or original-thinkers”

Makes me wonder???