Thinner oil provides better oil seal?

[autoreign]

I've read sometime ago that thinner oil has thicker oil film thickness (at low to mid load) around piston rings due to better flow and thereby providing better seal and better protection. Conversely, thicker oil provides thicker oil film thickness at extreme load (track day, racing).

It is unfortuanate that I could not find the document (a thesis from a university) and I could not find it on the net again.

Could anyone verify this being correct or not?

 

[StevieC]

It depends on the engine design IMO. Some Dodge & Honda engines I have encountered have better ring seal with a 20wt oil versus a 30wt oil.

I have seen other engines that consume oil on a regular basis (1 quart / 1000 miles) with 30 & 40wt's but when a 20wt is used the consumption stops completely.

 

[d00df00d]

Originally Posted By: autoreign
I've read sometime ago that thinner oil has thicker oil film thickness (at low to mid load) around piston rings due to better flow and thereby providing better seal and better protection. Conversely, thicker oil provides thicker oil film thickness at extreme load (track day, racing).

It is unfortuanate that I could not find the document (a thesis from a university) and I could not find it on the net again.

Could anyone verify this being correct or not?

This is from a Shell document comparing a 5w-20 to a thicker dino oil. All 5w-20s have at least some synthetic component in them (to keep volatility down), whereas the thicker oil was all dino. That's why the 5w-20 retained its viscosity around the piston rings better.

If you compared, say, a 5w-30 to a 5w-40, both with the same kind of base stocks, you would not get the same result.

 

[autoreign]

Originally Posted By: StevieC
It depends on the engine design IMO. Some Dodge & Honda engines I have encountered have better ring seal with a 20wt oil versus a 30wt oil.

I have seen other engines that consume oil on a regular basis (1 quart / 1000 miles) with 30 & 40wt's but when a 20wt is used the consumption stops completely.

Interesting. This could be the reason for the manufacturers to move towards thinner oil.


Originally Posted By: d00df00d
This is from a Shell document comparing a 5w-20 to a thicker dino oil. All 5w-20s have at least some synthetic component in them (to keep volatility down), whereas the thicker oil was all dino. That's why the 5w-20 retained its viscosity around the piston rings better.

If you compared, say, a 5w-30 to a 5w-40, both with the same kind of base stocks, you would not get the same result.

The article I have read was produced by an independance body who has no interest in yhe business at all.

Anyway, it is interesting that such test exist, bias or not.

 

[demarpaint]

Originally Posted By: autoreign
I've read sometime ago that thinner oil has thicker oil film thickness (at low to mid load) around piston rings due to better flow and thereby providing better seal and better protection. Conversely, thicker oil provides thicker oil film thickness at extreme load (track day, racing).

It is unfortuanate that I could not find the document (a thesis from a university) and I could not find it on the net again.

Could anyone verify this being correct or not?


Shell did a study showing that a 20wt oil did in fact do exactly what you're saying. In engines using oil due to bad "rings" would actually use less oil with a 20 grade than a 40.

 

[Gary Allan]

If you go over the works of Dr. Haas I believe you'll find the published SAE document that references better oil migration in the ring area with lighter oils vs. heavier oils.

 

[autoreign]

Great to see more supporting test/documents.

Thank you demarpaint and Gary Allan.

Gary would you have the link to Dr. Haas finding?

 

[Gary Allan]

http://www.bobistheoilguy.com/aehaas/

 

[autoreign]

Thank you Gary.

Getting to it right away.

 

[Gary Allan]

You could probably ask Dr. Haas what publication he was citing. It may take some time for filter through the entire works. Some of the conclusions are challenged, but there is still a substantial amount of good content to be digested.

 

[autoreign]

Hi Gary,

I went through the whole article. I was expecting more. Anyway good information.

Thank you.

 

[autoreign]

Originally Posted By: demarpaint
Originally Posted By: autoreign
I've read sometime ago that thinner oil has thicker oil film thickness (at low to mid load) around piston rings due to better flow and thereby providing better seal and better protection. Conversely, thicker oil provides thicker oil film thickness at extreme load (track day, racing).

It is unfortuanate that I could not find the document (a thesis from a university) and I could not find it on the net again.

Could anyone verify this being correct or not?


Shell did a study showing that a 20wt oil did in fact do exactly what you're saying. In engines using oil due to bad "rings" would actually use less oil with a 20 grade than a 40.

Thanks for sending me the article demarpaint.

I went through it and thought of giving a brief summary here for the benefit of others and also for the purpose of promoting discussion.

1) The article seem suggest that the oil flow on the piston rings pack is more likely to flow through the gap on each piston ring to get to the top ring. Hence, lower viscosity oil, being able to flow better, will provide a thicker oil film at bottom of the Top ring,

2) Oil consumption and blow-by is a function of gap width on each piston ring. When Gap on Top ring:Gap on 2nd ring is 3:1, it resulted in high oil consumption and high blow-by. When Gap on Top ring:Gap on 2nd ring is 1:3, it resulted in low oil consumption and low blow-by,

3) Piston deposit is a funtion of oil quality.

That is what I interpreted from the article (The article is mainly pictorial). Conventionally, it seem to suggest otherwise. I would really like to have some expert's opinion on this matter from all the gurus here (particularly on item 1) above.

Thanks in advance.

 

[Colt45ws]

Can I have this article as well? I don't see it posted here.

 

[autoreign]

Check your PM.

 

[vxcalais]

Why are oil manufacturers saying that thicker oil will reduce burning ? It goes against the grain. We have issues in Australia, Holdens burning oil at 10w30. I agree with the comment on it all being engine dependant. I dont think its a general rule.

 

[autoreign]

Originally Posted By: vxcalais
Why are oil manufacturers saying that thicker oil will reduce burning ? It goes against the grain. We have issues in Australia, Holdens burning oil at 10w30. I agree with the comment on it all being engine dependant. I dont think its a general rule.

Thank you for posting vxcalais.

This thread is to find out that thinner oil does, infact, provide better seal on the piston rings. In accordance to a article from Shell, it does seem that thinner oil does provide thicker oil film on the bottom side of the top piston ring thereby providing better oil seal.

Assuming that it does (which I have not witness one myself), I should think it will/might solve/reduce piston ring(s) leak; not solving leak on valve seals, shaft seals, and/or gaskets. So, you must first find out where is the leak on your Holdens.

Hope this answers your question.