Viscosity and retained oil film thickness

[Snoman002]

On a cold start (operating temp not ambient temp) is there any substantial difference in the thickness of oil remaining on internal components between say a 5w30 and a 0w20?

Reason being, LS motors are known to sometimes exhibit a cold start lifter tick. My engine, the AFM L76 is especially prone to it, which causes mass panic considering extended cold start ticking can be indications of the beginning of lifter failure (a somewhat common problem). Many will state that owners should go with a lighter weight oil so that it gets to the lifters faster (the tick is more likely to appear in colder weather). On the other side of the fence many claim a thicker oil will provide more protection until pressure builds.

For arguments sake lets keep "cold" to be north american average temps, call it no lower than 0 degrees F.

My personal experience, my current run of 10w30 PU has yet to tick (remote start, I use it obsessively) when based upon my previous OCI of 5w30 PP I would have expected to hear it at least occasionally by now. Granted, the weather has not been below the 30's yet. Current filter is a Fram ultra, previous was a Wix, for those who wish to argue the ADB side of things.

 

[aquariuscsm]

I'm with the "thicker oil will stay on parts instead of completely draining off" crowd,but to a degree. I feel you need to have a happy medium. Thick as possible/thin as possible,a perfect balance. Not too thick and not too thin. The 10W30 is probably perfect for your engine.

 

[A_Harman]

I've never had cold start lifter tick on my Camaro, and it has always had 5w30 in it (except for one OCI on GC, no lifter tick there, either). Lifter tick is caused by plunger sticking in the hydraulic lash adjuster portion of the lifter, and is probably not greatly effected by oil viscosity. Oil goes in there, and doesn't get out. If there is any varnish or sludge in there, it doesn't take much to cause the plungers to stick due to the very tight clearance.

 

[Shannow]

I'm not taken with the idea of thicker oil hanging around any better than thinner oil.

The bits and pieces that I've worked on over the years seem to indicate that there's a capillary action going on in things like rings and lifter/cam faces which hold/draw the oil to these points with the engine shut down, and that's there when the engine starts.

The statement that I've made before (and is oft co-opted to the theme of this thread), is that on start-up, this retained oil is many, many times thicker than the operational.viscosity, and can provide lubrication through hydrodynamics due to that higher viscosity...then thins down, and wear occurs in the middle, as the oil thins, before the ads get up and running.

 

[Merkava_4]

Originally Posted By: A_Harman
Lifter tick is caused by plunger sticking in the hydraulic lash adjuster portion of the lifter, and is probably not greatly effected by oil viscosity. Oil goes in there, and doesn't get out. If there is any varnish or sludge in there, it doesn't take much to cause the plungers to stick due to the very tight clearance.


What if the oil is thinner than what the lifter is calibrated for ? Those springs and check valves are designed around a specific oil thickness and my gut feeling tells me that if it's too thin, it'll get squeezed out of the lifter.

 

[Shannow]

Originally Posted By: Merkava_4
What if the oil is thinner than what the lifter is calibrated for ? Those springs and check valves are designed around a specific oil thickness and my gut feeling tells me that if it's too thin, it'll get squeezed out of the lifter.


Holdens in Oz used the SBC lifters.

They always clattered on 20W50 (even with STP in it), 25W60, and 30-70.

Holden's solution was to put a smaller volume filter on them to fill faster.

Clearly, ridiculously thick lubes weren't a solution.

 

[Merkava_4]

Originally Posted By: Shannow
Holdens in Oz used the SBC lifters.

They always clattered on 20W50 (even with STP in it), 25W60, and 30-70.

Holden's solution was to put a smaller volume filter on them to fill faster.

Clearly, ridiculously thick lubes weren't a solution.


Oil that's too thick won't get through the inlet hole fast enough. There's a happy medium in there somewhere when it comes to oil viscosity and hydraulic lifters. STP added to 20W-50 ? Really ?

 

[A_Harman]

Originally Posted By: Merkava_4
Originally Posted By: A_Harman
Lifter tick is caused by plunger sticking in the hydraulic lash adjuster portion of the lifter, and is probably not greatly effected by oil viscosity. Oil goes in there, and doesn't get out. If there is any varnish or sludge in there, it doesn't take much to cause the plungers to stick due to the very tight clearance.


What if the oil is thinner than what the lifter is calibrated for ? Those springs and check valves are designed around a specific oil thickness and my gut feeling tells me that if it's too thin, it'll get squeezed out of the lifter.


I guarantee that motor oil at ambient temperature will be many times thicker than the calibration fluid that was used to check the leakdown rate on the lifter. The leakdown test fluids are formulated to simulate viscosity at operating temperature.

 

[riggaz]

We see it on the VAG 1.4 16v engines that run on longlife servicing (507.00 504.00 5w-30). The lifters tick away until they pump up, when you switch them over to fixed interval and use a 15w-40 501.01 (one of the recommended grades on pre 2008 models) they no longer make any noise on start up and the engine is quieter.

 

[BrocLuno]

There is a cold start difference between 0W and 5W. Try the 5W and see what happens. Your engine is talking to you. Listen to what it says and act accordingly ...

 

[Snoman002]

Originally Posted By: A_Harman
Lifter tick is caused by plunger sticking in the hydraulic lash adjuster portion of the lifter, and is probably not greatly effected by oil viscosity. Oil goes in there, and doesn't get out. If there is any varnish or sludge in there, it doesn't take much to cause the plungers to stick due to the very tight clearance.


Even on cold start? I cannot see the oil remaining in the lifter when its sitting there for 8 hours with the full pressure of the valve spring pushing on it.

Originally Posted By: BrucLuno
There is a cold start difference between 0W and 5W. Try the 5W and see what happens. Your engine is talking to you. Listen to what it says and act accordingly ...


As I have, well from Dexos 5W to a 10W.

Originally Posted By: Shannow
I'm not taken with the idea of thicker oil hanging around any better than thinner oil.

The bits and pieces that I've worked on over the years seem to indicate that there's a capillary action going on in things like rings and lifter/cam faces which hold/draw the oil to these points with the engine shut down, and that's there when the engine starts.

The statement that I've made before (and is oft co-opted to the theme of this thread), is that on start-up, this retained oil is many, many times thicker than the operational.viscosity, and can provide lubrication through hydrodynamics due to that higher viscosity...then thins down, and wear occurs in the middle, as the oil thins, before the ads get up and running.


To clarify, you feel there likely no additional oil "hanging around" when using a thicker oil? Or conversely, that there is unlikely to be additional protection provided by a thicker oil before oil pressure has reached normal cold idle pressure?



To clarify, in my case the lifter tick lasts for a few seconds at most, almost certainly less than 10. I don't fear that this brief tick is likely causing any damage, but I do listen intently and pay attention to the duration simply due to the propensity for lifter failure in these cars. I only switched to 10W30 from 5W30 due to the availability of PUP, although if the tick remains at bay I will probably stick with what is working.

 

[Shannow]

Originally Posted By: Snoman002

To clarify, you feel there likely no additional oil "hanging around" when using a thicker oil? Or conversely, that there is unlikely to be additional protection provided by a thicker oil before oil pressure has reached normal cold idle pressure?


Point 1...I don't think that an oil that's 10cst at 100C is going to leave any more (and certainly not appreciably more) oil "hanging around" during drainback...it will always leave oil, I've never pulled apart an engine no matter how log it sat and not got oily.

On start-up, the thicker oil will have by it's nature thicker oil films when cold...simple physics.

Will this be of assistance during warm-up, when the surfaces move through the Stribeck curve from right to left and into the range where active additives are the driver ?

Can't claim that either.

 

[OVERKILL]

Originally Posted By: Snoman002


Even on cold start? I cannot see the oil remaining in the lifter when its sitting there for 8 hours with the full pressure of the valve spring pushing on it.


Only a certain number of valves are going to have valve spring pressure against them

 

[Shannow]

Originally Posted By: BrocLuno
There is a cold start difference between 0W and 5W. Try the 5W and see what happens. Your engine is talking to you. Listen to what it says and act accordingly ...


At -30C there is...

Not everyone starts their cars at -30C.