Thinnest oil to protect engine when warming up

[NGRhodes]

Say we have a common car engine, where an oil with a HTHS of 2.9, xW-30 SAE grade is thick enough to protect an engine when fully warm for general normal use.
Assuming a common generic additive pack, what is the minimum viscosity oil to adequately protect the engine as it warms up from a starting temperature of 0 degrees C ?

 

[RooflessVW]

I'm not sure I fully understand your question, but an SAE30 would do fine at 32°F

 

[NGRhodes]

Originally Posted by rooflessVW
I'm not sure I fully understand your question, but an SAE30 would do fine at 32°F


That's the thick end, I'm thinking about the thinnest - would a Xw30 with a KV0 and KV40 of 10cst be sufficient ?

 

[SandCastle]

The _minimum_ viscosity oil that would protect in cold start at 0C/32F would be SAE 0W-30. The maximum viscosity oil would be SAE 20W-30 - if such an oil is even sold. And as rooflessVW pointed out, even a monograde SAE30 is arguably 'adequate' in this scenario, although not fuel efficient.

 

[dubber09]

5w30 or even 10w30 are more than good for that.
10w oils have pour point at about -40C.

 

[NormanBuntz]

I'd go with whatever the owner's manual says. Why guess?

 

[FCD]

The truth is in abive freezing temps, even Monograde oils will flow quickly enough when cold to protect the engine adequately.

 

[oil_film_movies]

At 0 degrees C, all oils (0w16 and higher visc ratings) are too thick.
All will protect at start-up cold 0 degrees C, and the thinner ones will protect better at start-up.
Theoretically, I'd say you always want to start an engine at 30 cSt. Real oils are always thicker than that at 0 degrees C.
For example, I'm currently using Eneos Racing Street 0w20 which is very thin at KV40, 29 cSt. Note that is KV40, not KV0. At KV0, the viscosity is pretty high.
For the Eneos example, at 0 degrees C its at about 200 cSt, still too thick, but thats the thinnest stuff around.
See https://wiki.anton-paar.com/en/engine-oil/

 

[Bryanccfshr]

As long as the oil is flowing and pumpable the best way to reduce wear on warmup is to warmup as quickly yet gently as possible so that the antiwear additives activate.
Start the vehicle and begin driving. The perfect scenario would be to start up by an on ramp and accelerate gently to highway speeds and cruise.
Regardless of viscosity it will take 15-25 minutes of highway cruising from cold-start for all the fluids to reach equilibrium. If you spend most of your driving time in that window that is where lower viscosity oils save fuel. The further along that window you go, the less savings and then you start dealing with the negative consequences.

 

[Dyusik]

There is enough oil left over from the previous day/week/month when it ran to protect the parts until the oil is pumped up. Flow of oil is a scary thing only in a fresh build or to a simpleton that dumped a bunch of solvent down the fill hole to "de-sludge" an engine.

 

[Linctex]

Originally Posted by SandCastle
The maximum viscosity oil would be SAE 20W-30 - if such an oil is even sold.


Most all modern SAE 30W oil could easily be marketed (accurately) as 15w30 or 20W-30

 

[Shannow]

Originally Posted by oil_film_movies
At 0 degrees C, all oils (0w16 and higher visc ratings) are too thick.
All will protect at start-up cold 0 degrees C, and the thinner ones will protect better at start-up.
Theoretically, I'd say you always want to start an engine at 30 cSt.


At 0C ?

Rubbish.

Everything (probably including SAE30) is well within it's pumpable range, and will get where it needs to go at about the same … it's replacing air in the galleries, and being sent there by a positive displacement pump...again, well within it's pumpable range.

Got to remember a couple of things
* engines aren't "dry" when you start them
* PD pumps move the same volume per revolution.
* Pumpable oil is that which can replenish the suction line at the same rate that it is moved by the pump.

Remember also that the Sequence IVA wear test is chosen to be the point that all that excess viscosity is diminishing, and the additives aren't fully functional. Per bobbydavro, he's done sequence IVA at a lower temperature (thicker oil, less additive activation), and higher temperature (less viscosity, more additive activation), and the point chosen is the sweet spot.

A 10Cst oil at freezing temperatures (optimum per the now defunct University 101, LOL) would only work if the additives were all fully playing ball at that temperature...i.e. it's not what happens...that "excess" viscosity is helping you in the cold (*)

(*) before anyone jumps, this is NOT advocating SAE40 for the OP, just dispelling another BITOG myth that won't die.

 

[NGRhodes]

Originally Posted by Shannow

A 10Cst oil at freezing temperatures (optimum per the now defunct University 101, LOL) would only work if the additives were all fully playing ball at that temperature...i.e. it's not what happens...that "excess" viscosity is helping you in the cold (*)

(*) before anyone jumps, this is NOT advocating SAE40 for the OP, just dispelling another BITOG myth that won't die.


What I was pondering over, how much cSt is needed to protect due to the reduced usefulness of additives at 0C and as the engine warms.

 

[fdcg27]

Originally Posted by NGRhodes
Originally Posted by Shannow

A 10Cst oil at freezing temperatures (optimum per the now defunct University 101, LOL) would only work if the additives were all fully playing ball at that temperature...i.e. it's not what happens...that "excess" viscosity is helping you in the cold (*)

(*) before anyone jumps, this is NOT advocating SAE40 for the OP, just dispelling another BITOG myth that won't die.


What I was pondering over, how much cSt is needed to protect due to the reduced usefulness of additives at 0C and as the engine warms.


It is a happy accident that even a 0W starts out a lot thicker at the freezing point of water than it will end up at the boiling point of water.
It seems to me that the excess viscosity will protect the engine as the oil warms to the point that the add pack becomes effective.

 

[gfh77665]

Originally Posted by Dyusik
Flow of oil is a scary thing only in a fresh build or to a simpleton that dumped a bunch of solvent down the fill hole to "de-sludge" an engine.



LOL!

 

[CT8]

What do you mean by thin oil protecting the engine when cold? The ability to pump? The oil being able to keep the parts separated?

 

[NGRhodes]

Originally Posted by CT8
What do you mean by thin oil protecting the engine when cold? The ability to pump? The oil being able to keep the parts separated?


Anything that does not cause damage or excessive wear referenced against the active additive pack.