esters affect seals?

[neo3]

I read on here somewhere that HM oils have seal conditioners which are based on esters (true?). Does this mean that esters cause rubber seals to swell? For my low mileage car with no leak problem I'd prefer to not use anything that makes the seals swell, so should I avoid anything with esters?

 

[Solarent]

Yes some seal conditioners do have ester content. But all liquids (fuel, oil, mixtures etc) can impact seal materials - it all depends on what the seal is made of and how the chemicals in the oil (not just esters) affect those seals.

In the API 1509 Chart G-6 it lists the required bench tests that all current engine oils (that meet API SN) must undergo in order pass the seal compatibility requirements. All registered oils will have met this standard which is agreed on by the OEM's so I think that as long as you use an oil as recommended by your OEM (likely ILSAC GF-5 or API SN) then you should be good. If you are going to use something that doesn't meet those specifications you may want to contact the oil company and see if they will supply you with the data on elastomer compatibility and compare it to limits on the G-6 Chart. (the chart provides a list of the ASTM tests that you would be asking for and the elastomer materials that the oil should be tested against).

Short answer - no you shouldn't avoid things just because they have esters, but be careful with oils that don't meet API specifications.

 

[OneEyeJack]

I think that all this depends on the total package in that bottle. I have a V8 4Runner that has about 150K miles of hard use in a desert environment with heavy towing on unimproved dirt roads and I use Red Line 0w-30 with 10K OCI's that is an ester based oil. The level on the dipstick does not move any amount that I can detect between changes. This is a bit beyond the 70-90K mileage recommendation of some high mileage oil manufacturers. If there was going to be a problem it should have appeared by now.

 

[SonofJoe]

It was before my time but if I recall correctly, when the first synthetic oils came out, it was found that PAO's shrink or 'dry out' certain seal elastomers. This caused engines to leak oil. Subsequently a small amount of ester (which has the opposite effect of swelling seals) was added to the PAO oils to counteract things.

High mileage oils contain a very small amount of ester which attempts to swell things like valve seals to keep them tight. Personally I wouldn't worry about it. There are lots of other things in oil that aren't great for seals such as ashless dispersant. If the oil formulator has done his job properly and passed all the relevant tests, your engine will be fine.

 

[Boss302fan]

I thought all syn oils have esters?

 

[SonofJoe]

Originally Posted By: Boss302fan
I thought all syn oils have esters?


Not necessarily. Synthetic oils based primarily on PAO (eg European 0W30's) generally must contain some ester for seals. Synthetics based on Group III (Hydrocracked) base oils generally don't need to contain ester as the base stock is relatively benign towards seals.

Not sure what's current common practice with PAO/Hydrocracked blends but I made myself one to use in my old Daihatsu based on 30% PAO with the balance being Hydrocracked and I didn't feel there was any need for ester in the blend so I left it out.