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Mar 2, 2003
So Cal
found this on the net. is this basically correct? YEARS ago when syntheitcs were introduced to the market there were seal swelling problems giving a bad rep to synthetics that perpetuates even today, simple chemistry changed this very quickly. There is a HUGE differences in one respect between conventional and fully syntheitc lubricants...WAX. In a conventional oil the molecules vary greatly in size and have a good pobability to sludge. As a gasket ages (due to heat and solvents) it dries and sludge build up prevents seal swelling components from reaching the seal (thus it cannot get revitalized). Cracks eventually result in an old and dry gasket...waxes and sludge CAN plug the small cracks preventing leaking. Adding a syntheic to a seal that has aged will, with syntetic oils improved solvency and detergency, dissolve sludge buildup. Combining the sovency and detergency with more consistant molecular size, leaking MAY occur. An engine that is well maintained with timely oil changes will tolerate a change to synthetics at any point is it's life.
Thanks for bringing this up. I was too scared to ask this over at the "question of the day" forum because those guys are way above my league. One of the answers that Mola gave was that ester based oils cause seal swells. But, don't today's synthetics have esters in them too. Mola mentioned that a good pao/ester combination will prevent seal swell. Man, I'm really confused. How do we know that brand X has the right balance to prevent seal swell? The more I learn, the more nervous I get????
My 1987 Mitsu Mighty Max pickup got switched @ 150K mi. No leaks, no consumption. It always got 3-4K changes with Havoline 10W-40. It consumed about 1/2 qt. of Havoline beyond 3K. Consumption with Syn is nil and no leaks. I believe the Statement, but I have to limit it to Castrol Syntec and Mobil 1, because these are the only two I have used in an older vehicle. I don't believe these two to be a problem in any vehicle that has been well maintained with a quality dino before. If the seals be ruined by poor dino and or neglect, then any good syn or hdeo might make leaks worse.
Moved to Shaeffer's 7000 on a SAAB 4cyl turbo with 118000, no leaks, and the thing hasn't used a drop of oil over the last 4kmi.
Seal swell in petroleum based motor oil is a basic property of the rubber (Buna-N,Poly-Acrylic, Vamac, etc.) and the standard % is a factor in developing the seal lip diameter. If the seal is used in an application where the fluid does not induce swell, then an additive is required. Molakule explains the issue in this thread - Seal Swell
One area I have always worried, is with a product like Max life that has a seal sweller in it, and if you are using in in an engine thats near new, over time what effect would this have? There seems to be a tacky image linked to the after market add in brands of oil treatments, but what would be the long term effects of having a seal swell treatment in the oil from day one?
Originally posted by Francis: One area I have always worried, is with a product like Max life that has a seal sweller in it, and if you are using in in an engine thats near new, over time what effect would this have?
My understanding is that Maxlife (and likely the other "high mileage" oils) has a seal "conditioner," that is, rather than swell the seals, it is a balanced fomula that restores some of the pliability to old stiffened seals and would maintain the pliability of new seals. Anyway, I am using Maxlife in my 70,000 to 110,000 mile non-leaking vehicles and am not the least worried. Supposedly Maxlife can reduce or eliminate some oil leaks. Presumably this is by softening hardened seals so they can better fill the intended gap. BTW, you folks have Maxlife, but is it like in Europe (I saw on the website) where it comes only in 10w40 and 15w40? I wish we had it in 15w40. I am going over to Durablend for the summer in one vehicle to get a 15w40.
I believe all current synthetics have enough esters in them to not cause problems with a switchover. But if you feel you might have problems, first use an autoRX treatment to clean and condition the seals. All oils have different reactions with different seal materials. In the industrial arena this happens with the terrible seal properties of napthenic oils used in refrigeration systems. The reaction is different with different seal materials. When switching an Ammonia Compressor over from traditional napthenic oil to a hydroprocessed oil, most of the seals begin to go back to normal, causing some leaks if they are in bad shape.
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