How much engine wear occurs after warm up?

[Threeofnine]

From my understanding practically all engine wear occurs at cold start and until operating temperature is reached. Does any real wear occur after everything has reached operating temperature or does the oil film pretty much eliminate all metal to metal contact? For example, would there be any real engine wear from a 1000 mile drive on the highway where the engine was never allowed to cool down?

Assuming fresh oil and good maintenance of course.

 

[BigCahuna]

Being most cars that people own nowadays make it over 250k miles, and they are started alot in that mileage range, I would venture a bet most wear occurs from not changing oil when it should be.,,,

 

[oil pan 4]

Almost none. Most of the wear happens at the rings because of dirt and carbon abrasion.
I was reading a pointy head paper about how modern gasoline engines only make about 1mg per mile of oil contamination driving on the highway. Nearly all of that is combustion byproducts and dirt that gets by the rings and down into the oil.

 

[gman2304]

Almost none

^

 

[ripcord]

There is always some wear going on while the engine is running, but it's true that certain types of wear is much more rapid before the engine is warmed up, especially the cylinder rings and bores. This is one reason why over the road trucks can last a million miles between overhauls. They often get driven 500 miles or more between cold starts. This is the reason why oil viscosity is a non-issue in terms of start up wear.

I believe the chart below is from the famous 1950's SAE paper on how engines wear.

 

[BISCUT]

Being most cars that people own nowadays make it over 250k miles, and they are started alot in that mileage range, I would venture a bet most wear occurs from not changing oil when it should be.,,,

Where did that information come from?

 

[fantastic]

From my understanding practically all engine wear occurs at cold start and until operating temperature is reached. Does any real wear occur after everything has reached operating temperature or does the oil film pretty much eliminate all metal to metal contact? For example, would there be any real engine wear from a 1000 mile drive on the highway where the engine was never allowed to cool down?

Assuming fresh oil and good maintenance of course.

Wear doesn't stop happening but the rate of wear can change depending on the conditions. Highway miles in at least moderate temperatures are going to be some of the lowest.

 

[IndyIan]

I think most manufacturers(in N.A.) are pushing the limits of low viscosity oils maintaining the hydrodynamic wedge in plain bearings in some engines and maybe in all timing chains? Especially with the low rpms they run. Its my understanding this is why the first RAM ecodiesels failed so often and so fast. RAM tried just spec'ing thicker oil as fix but it took more than that really solve the problems of keeping the rod bearings alive.
Once the wedge gets too thin, then wear can happen at much higher rate than with a thicker wedge, and also if you have any particulates bigger than the wedge thickness, things go bad fast as well.
This is also why motors in race engines use higher vis oils as well as in engines run hard continuously, as higher temps equal lower viscosity and thinner hydro wedges just as the loads on the bearings is high due to high rpms.

 

[TheOilWizard]

Being most cars that people own nowadays make it over 250k miles, and they are started alot in that mileage range, I would venture a bet most wear occurs from not changing oil when it should be.,,,

Not a bad guess, but I'd also include engines running low on oil. People don't check oil levels anymore.

 

[edyvw]

UOA from my BMW:
One with 5,000mls has a lot of track time, including 1 1/2hrs sessions (without pit stop) at 5,100ft altitude and 102f ambient temperature.
The other one is 4,600mls only for winter driving, 60% at least HWY to ski slopes and back. Both are min HTHS 3.5cP, so not energy conserving. As you can see, wear is almost the same, although track one was spinning 5-7,000rpms for a lot of miles.

 

[ryster]

Where did that information come from?

Yeah, seems a bit optimistic. This recent article paints a slightly different picture. There will always be outliers in data, and there could have been some in the data sample with 250,000 miles, but the overall averages are much less than that...

https://autorecyclingworld.com/what-is-the-lifespan-of-a-vehicle-in-the-usa/

 

[Exhaustgases]

If it is set in its ways of say 10k plus miles and has some decent viscosity oil with a bit of EP, and no over rich condition, the wear will be non existent. The killer will be low viscosity oils, that freely run off the surfaces after shut down, unless a prelube system is installed.

OOPS you said after warm up. No wear to un measurable wear, with clean and proper viscosity oil, unless there are extreme metal to metal contact high pressure areas like cam n tappet interface .

 

[MRC01]

From my understanding practically all engine wear occurs at cold start and until operating temperature is reached. Does any real wear occur after everything has reached operating temperature or does the oil film pretty much eliminate all metal to metal contact? ...

Generally true but it depends on how you drive. If you're competing in SCCA using full power extensively and banging off the rev limiter you will get more wear than cruising down the freeway.

That said, the worst thing you can do to a car is drive it infrequently, and when you do drive, short 5-10 mile trips around town never giving it a chance to get to operating temperature long enough to boil off moisture.

 

[BigCahuna]

Where did that information come from?

Go to your local used car lot and read mileages for yourself.,

 

[Chris142]

Not a bad guess, but I'd also include engines running low on oil. People don't check oil levels anymore.

Those of us on this forum not included.

 

[BISCUT]

Go to your local used car lot and read mileages for yourself.,

Ahhh, now we know.

 

[CharBaby]

Less than when cold!

 

[TheOilWizard]

Those of us on this forum not included.

Hey, you might actually be surprised

 

[Escape08]

I think you got the question in reverse. Is it before warm up? Engine wear start a few seconds after the engine starts

 

[ripcord]

Ahhh, now we know.

He's not wrong. 300k is the new 100k.