Does anyone have any idea how long a protective layer of oil stays on the engine parts after shutdown? I am not talking about enough oil for a lubed start. I am just talking about a thin film that would prevent rust from starting. This is on a car that is not driven much. I drive it ocassionaly to keep the battery charged and burn off any water that may have condensed in the oil. I am now wondering at what point does the engine become totally dry and rust can set in. I would think it would be in the order of days or weeks because whenever there is oil where I don't want it never makes sense to think the part will just drip dry and be oil free, ever. With the engine being hot on shut down I can see it keeping the oil that remains hot and much more likely to just run off so I don't know.
How long does an oil film stay on engine parts after shutdown
- Thread starter BrianApp
- Start date
Seen torn down engines that had sat in junk yards outside (in engine bay and not rained on) for quite awhile and don't really have any rust inside them. I think an engine would have to sit a long time without being ran in a very humid environment to start causing internal rust.
How often are you driving it, and does it get to full operating temperature for awhile?
How often are you driving it, and does it get to full operating temperature for awhile?
Forever. It will never fully drain off.
I've seen engines my brother had on engine stands over the years that had a thin film of oil on the cylinders/valve train for well over a year [ a few longer than that] when he/we pulled the heads off to rebuild/replace/swap or whatever it was he wanted to do to the engine. There was no flash rust whatsoever inside those engines.
Use oils with ester and/or moly.
They stick to metal better.
I said better to have an escape route in case anti-moly members get excited.
or use oils with moly if the ester kind is pricy.
If you got a fancy car parked in the garage, you probably can afford oils with both.
They stick to metal better.
I said better to have an escape route in case anti-moly members get excited.
or use oils with moly if the ester kind is pricy.
If you got a fancy car parked in the garage, you probably can afford oils with both.
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I'm using Castrol Magnatec right now, and it has special polar molecules designed to attach to the metal surface and not drain down.
I like intelligent molecules and currently using it in one of my older cars. this car has a $4/qt budget for oil. I may reduce the budget for this car to ST or Kirkland levels but Castrol GTX Magnatec Full Synthetic 10W30 has a 6.1 Noack that not many can beat or match. Not even fancy oils.
Right now I'm using the Magnatec 5W30 full synthetic, but to be honest I found the Magnatec 10W30 semi-synthetic to be smoother. I'll probably go back to that next time.
As has already been mentioned the oil film persists for a very long time and it has little to do with intelligent or unintelligent molecules. Under worse-case conditions the film will eventually drain down to a monolayer which is self-repairing. But in most areas of an engine the persistent film is far thicker than a monolayer.
I like the GTX Magnatec 10w30. I've used it in 2 cars and it hardly burned any.
ignoring what's really in there or the marketing, the new jugs in U.S. say Full Synthetic for the past couple(?) of years. I think in old days, they may have said semi syn. Do they say semi on them Down Under?
I agree. The engines I referenced were from the late 1960's to mid 1970's. At the time oil had stupid molecules, not the "intelligent" molecules smart marketing departments named them to sell more oil. Don't get me wrong, the oil today is better, but the oil of yesteryear stayed put for a very long time.
In Australia we have a lot of different types of Magnatec
0W20 full-synthetic SN & GF-5
5W30 full-synthetic SN & A3/B4 (what I’m using now)
5W30 full-synthetic SN, A5/B5, Ford 913-D
10W30 semi-synthetic SN & A3/B4 (my favourite)
5W40 full synthetic SN & A3/B4
10W40 semi-synthetic SN & A3/B4 (the original)
5W30 DX full synthetic SP, GF-6, Ford 921-A / 946-B1 / 961-A1, Dexos1-Gen2
15W40 semi-synthetic SN/CF & A3/B4
5W40 full synthetic SN/CF, C3, Dexos2
5W30 SUV full synthetic SN/CF, ACEA C3, MB 229.51, Dexos2
Depends on the engine & oil. Aircraft engines start to rust internally if they sit more than a couple of weeks. But their oils aren't overbased with elements like Calcium to neutralize acids, and they don't have other beneficial additives that car oils do.
Oils of yesteryear were thicker, which helps them stick to engine parts longer before drooling off due to gravity. Newer oils have those magic intelligent molecules trained to stick to engine parts longer
That said, the worst thing you can do on a infrequently run engine, is start it and let it run for a few minutes "to cycle the oil" then shut it off. This won't run long enough to achieve operating temperature, so it won't vaporize condensation and it will only create more combustion byproducts to wreak their havoc on the engine internals. If you run the engine, run it long enough to fully warm up and reach operating temperature, on an actual duty cycle moving the car, not just idling.
Oils of yesteryear were thicker, which helps them stick to engine parts longer before drooling off due to gravity. Newer oils have those magic intelligent molecules trained to stick to engine parts longer
That said, the worst thing you can do on a infrequently run engine, is start it and let it run for a few minutes "to cycle the oil" then shut it off. This won't run long enough to achieve operating temperature, so it won't vaporize condensation and it will only create more combustion byproducts to wreak their havoc on the engine internals. If you run the engine, run it long enough to fully warm up and reach operating temperature, on an actual duty cycle moving the car, not just idling.
Why don't aircraft engine oils use some of the beneficial additives that PCMOs have?
So, as I thought, most people agree that an oil film will stay on the engine parts for years if not forever. I am wondering then why a small engine that I have seized hard in place after 5+ years of non use. I can't get the thing to move. Now I make it a practice to turn my model engines over by hand several times yearly. So the same thing can happen on a full size car engine? If an oil film remains on the engine how can it seize up?
They are totally different but one poster said it happened to his car engine. At the end of the year I take my model engines off and coat the internals and fill the crankcase with marvel mystery oil to stop bearing rust and seizing.