Seal swelling - Synthetic oil vs. Conventional

[OilUzer]

Assumption:
All oils cause seal swelling (conditioning?) and it's not a bad thing. It's the way it is ...

Q:
is it true that in the old days (not sure about the time frame) synthetic oils used to cause less seal swelling (compared with conventional) and that's why it caused more leaks mainly in older cars.
Eventually synthetics were improved (by adding ester?) to enhance swelling (comparable to conventional) and as a result, today's synthetic oils do not cause as much leak as they used to.

Any truth to any of the above?

 

[Donald]

I would not assume conditioning is the same as swelling.

 

[OVERKILL]

PAO tends to dry out seals, so an oil with a PAO base is often dosed with POE or some other ester to counter that effect. All oils contain additives to aide in keeping seals "fresh" and pliable, not swelling them.

 

[Kestas]

I asked our seals engineers how synthetic oils affect their product. They said their seals are tested in the lubricant that is specified for use. They don't do extra testing for synthetic with seals specified for use with regular oil.

 

[doitmyself]

Is it reasonable to assume that many of the early leaking engine anecdotes in the 70's was also possibly due to better cleaning ability of the newly introduced synthetics? Oil deposit material on the seals getting cleaned off and resulting in leaks?

 

[forkian]

I have been running PPHM for 30,000 miles (7k OCI) in a 2007 G6 GTP 3.6. Had no leaks at a about 100,000 miles. Now it has blue smoke at start up. I'm thinking maybe it didn't really need High Mileage oil and this could have caused leak issues with the valve seals, allowing oil into the cylinder?
Considering adding some Lucas oil treatment, but not too sure yet.
I would recommend not using High Mileage oil as a preventative measure, as I did. It could cause some issues instead of preventing them.

 

[The Critic]

During a recent cylinder head gasket replacement on my Prius, I found the valve cover gasket to be extremely soft and pliable after 185K miles. However, the 5 internal oil passage o-rings and the internal VVT gasket were all hard….almost as hard as a rock. This engine received 10K oil changes from 0-90K using 0w-20 synthetic, then 5K oil changes from 90k-185K miles using mostly 0w-20 synthetic. Just another data point - not sure if HM oil could have helped here.

 

[bbhero]

How on Earth would a HM oil cause oil leak in valve seals???

I bet that blue smoke burning issue is from something far far removed from using a HM oil.

I may be wrong...

 

[wemay]

If the oil meets SN/SN PLUS and your vehicle requires those specs, the oil must fall within the accepted range for all ingredients permitted by the specs it meets. The rest is just bunk.

 

[dave1251]

Originally Posted by forkian
I have been running PPHM for 30,000 miles (7k OCI) in a 2007 G6 GTP 3.6. Had no leaks at a about 100,000 miles. Now it has blue smoke at start up. I'm thinking maybe it didn't really need High Mileage oil and this could have caused leak issues with the valve seals, allowing oil into the cylinder?
Considering adding some Lucas oil treatment, but not too sure yet.
I would recommend not using High Mileage oil as a preventative measure, as I did. It could cause some issues instead of preventing them.



If this was an oil related issue then any motor oil would cause the issue. PPHM is API certified thus it had the same seal conditioning requirements all API certified oils have.

 

[OilUzer]

Originally Posted by Kestas
I asked our seals engineers how synthetic oils affect their product. They said their seals are tested in the lubricant that is specified for use. They don't do extra testing for synthetic with seals specified for use with regular oil.


Interesting!
Are the new oils (syn or blend or dino) backward compatible? Let's say you have an old(er) car with different kind of seal material ... Who tests for that and is there a compatibility / performance test for seals?

Back to my original post, I had heard rumors that syn oil can be hard on seals and may cause swelling, etc. No proof but what you hear or read here and there ...
My recent and very limited research shows the opposite as far swelling. Meaning that conventional oils cause more swelling and the synthetics had to catch up!

 

[caprice_2nv]

I've run nothing but synthetic in my 76 Oldsmobile 350 since 2007. It was taken from the junkyard and we put all new gaskets and seals (except head gaskets) and it has the cheapest chrome valve covers on it that typically have sealing issues. 100k miles later and 12 years (it is parked all winter outside in cold weather) and no noticeable oil leaks yet.

My 83 Caprice leaks a lot but I imagine it would be regardless of oil after 36 years and 235k miles. Valve cover gaskets are the worst but these cars are known for that.