Possible advantage of high old viscosity oils

[DrRoughneck]

Let's say you drive your car daily to work. Come home at 5, park it in the driveway until 8 in the morning the following day when you leave for work again.
So everyday, your engine is turned off, sits for 15 hours, then gets turned back on again.

As the engine cools down through the evening and gravity pulls the oil back down in the pan, a higher cold viscosity oil (like a 10W30) which drains slower would not have time to drain down as much as a 0W30. More of the oil would still "stick" to the upper moving parts than with an oil of lower cold viscosity.

It may sound counter-intuitive, but now thinking about it that way, wouldn't it make more sense to adopt a higher cold viscosity oil (like a 10W30) in order to reduce cold-start wear, if the usage pattern is (reliably) 15 hours between engine runs?

 

[kschachn]

The temperature of your engine and the oil at shut-off is high and will remain warm for some time depending on ambient. Unless a large amount of oil is still undrained when your engine (and oil) reaches well below zero, the two oils will behave in a very similar fashion.

At any oil temperature above zero there isn't much difference.

 

[Quattro Pete]

Originally Posted By: DrRoughneck
As the engine cools down through the evening and gravity pulls the oil back down in the pan, a higher cold viscosity oil (like a 10W30) which drains slower would not have time to drain down as much as a 0W30. More of the oil would still "stick" to the upper moving parts than with an oil of lower cold viscosity.

Vast majority of both oils will flow back down to the pan while the engine (and oil) is still warm. Or to put it another way, when warm, both 0w-30 and 10w-30 have roughly the same viscosity so they should flow roughly the same.

And both oils will leave a thin film on all engine internals, even after 15 hours.

 

[DrRoughneck]

Ok then.

 

[Quattro Pete]

But if you buy into Castrol's marketing, their intelligent molecules in Magnatec cling to engine surfaces better.

 

[SR5]

Yes Castrol Magnatec has an add that clings to metal surfaces and reduces drain back (at the molecular level).

It's also an affordable and well respected name brand oil that carries all the specs most people require. The semi-synthetic 5W30 Dexos is producing great UOA's right now, low iron wear numbers and good viscosity retention.

 

[nascarnation]

Here's your chance to be a BITOG hero.

Run an OCI with 10W30 (or thicker..maybe 20W50) and another with 0w20. Probably a good idea to use same brand and type. Make sure the seasonality is comparable (don't do one in summer and the other in winter).

See how the UOAs compare.

Let us know.

 

[ShotGun429]

I commonly take apart auto and tractor engines that been setting 50 plus years undisturbed and rod and main bearings are still coated with active oil film...cylinder walls are a different story.

 

[fdcg27]

As someone once wrote, an engine is an oil environment and you find oil everywhere even in engines that have seen decades of disuse.
The cylinder bores are indeed another matter and that's why the rings can rust to the bores after decades of sitting.