Originally Posted By: LeakySeals
Originally Posted By: Danh
Originally Posted By: LeakySeals
Your not pouring form-a-gasket in your engine. Your slowing a leak using an oil thickening additive, swelling old shrunken seals with a seal swelling additive, or both. When you stop using a seal swell additive, the seal shrinks back to where it was and the leak returns. Whether its a separate additive or part of HM oil, this will happen if you stop using it. Because seal swelling is not permanent, only lasts as long as a swelling additive is in use. May be less hassle and cheaper cost to use a HM oil that already has a seal sweller as part of its additive pack.
I thought HM oil contained seal "conditioners" rather than seal "swellers". As I understand the difference, conditioners maintain and restore a seal's pliability while swellers actually make it larger. Swellers can be problematic as they also swell seals that don't need it. Conditioners just try to make the condition of the seal more like it was when new. All oils contain conditioners, HM oils just have more. I think...
That's what I thought for the longest time too. But I have since changed that view. Partly on personal experience, partly on research. Here's what I think, take it for what its worth. Because we don't know what High Mileage oil "conditioner" really means and what makes it different from the conditioner in a regular oil.
I've been on and off HM oils with leakers and oil burners for several years. External leaks always return when I stop using HM oil. Not immediately but gradually over the course of a subsequent oil change. Something wears off. The generic claim is High Mileage Oil has a special "seal conditioner" that makes old hard rubber soft and pliable again. If that's all there is to it then why does the leak gradually return within 3-5k miles when I stop using HM oil? Would think "soft and pliable again" is more of a permanent fix and seals should not become hard and brittle almost right away.
There has to be more to it. All modern motor oils have some level of conditioner, why isn't that enough? Researching rubber gaskets there is a natural aging called "outgassing". A hardening and shrinking process as rubber loses the chemicals that make it porous and flexible. Can a conditioner reverse the aging process, put the chemicals that caused the outgassing/hardening/shrinking back? Don't see how that's possible. Can a conditioner prevent a future leak? Maybe slow the aging process but its still going to leak eventually.
What else is in a HM oil seal conditioner that stops leaks a regular motor oil seal conditioner can't? Sweller is a scary word as indicated by your reply. Conditioner is a word that doesn't scare people, sounds like a good thing. The word corporate marketing would choose. Mobil 1 High Mileage claims a "Seal conditioner to help prevent leaks and reduce oil consumption". If you go to Mobil 1's website they actually use the word sweller and swells on the website FAQ. Maxlife uses words like "special seal conditioners" and "seal conditioning agents". On the Valvoline Maxlife FAQ you find the phrase "stop leak additives". Pennzoil High Mileage uses "special conditioning agents and additives to help stop leaks from seals and reduce the oil consumption that is typical of older, worn engines". Tap dancing? Misleading? All the jargon makes me suspicious. Only one uses the word, but IMO a swelling agent is in use with all of them.
You may very well be right. In any event, people seem to switch to and from HM oils without consequence except for reappearance of leaks.
What effect do you think HM oils have on RTV seals? These things seem to be everywhere and I thought RTV was impervious to pretty much anything. If you have a leak in a modern car odds are pretty good it's from an RTV seal, I guess.
