Synthetic oil?

Romeo wrote: It's all nonsense.

Or is it?

From what I understand, "sludge" from dino oil collects around gaskets and seals (and other places). The reported problem with synthetic oil is that is washes these sludge deposits away from around these (and other) areas. Washing sludge away is not necessarily a bad thing, but it IS a bad thing if the sludge itself is helping to prevent oil from leaking from worn seals and shrunken/cracked gaskets.

It is widely reported that many people DO have problems with oil leaks when they switch over to synthetic oil on an older car, especially one with high mileage.

Having said that, I started using synthetic oil on my '86 GT (190,000 KM) when I bought it three years ago and I haven't had any serious leaks.

Romeo wrote: There should still be detergents in any half decent non-synthetic as well. From everything I've learned about oils (And I've done alot of reading up on them), the difference is in molecular stability, nothing more.

Sign up at Pennock's and console all the guys who've reported oil gushing out of their engines with that info.  

Romeo wrote: Besides, people also say you couldn't go from full synthetic back to conventional...

...

I've never heard that before.

Romeo wrote: One of the most common wives' tales out there. Once you're go to synthetic, you have to go completely. You can't mix, and your engine is supposed to 'adapt' to the higher quality oil.

That's ridiculous, as there's nothing to back up an old wive's tale like that (which I've never heard). Synthetic "blends" (mixed synthetic and dino oil) are marketed and sold.

However, engines leaking oil when switched over to synthetic has been reported time and time again. Certainly not in every case, and probably only in a small percentage of cases, but it does happen.

Robin, don't rely on information bandied about by Tristan or myself. Google it and draw your own conclusions.

Patrick wrote: Romeo wrote: One of the most common wives' tales out there. Once you're go to synthetic, you have to go completely. You can't mix, and your engine is supposed to 'adapt' to the higher quality oil. That's ridiculous, as there's nothing to back up an old wive's tale like that (which I've never heard). Synthetic "blends" (mixed synthetic and dino oil) are marketed and sold. However, engines leaking oil when switched over to synthetic has been reported time and time again. Certainly not in every case, and probably only in a small percentage of cases, but it does happen. Robin, don't rely on information bandied about by Tristan or myself. Google it and draw your own conclusions.

Kinda strikes me of the whole 'Toyota Gas Pedal' thing: I've just learned to ignore people's reports when it borders on mythical levels of explanations sans scientific study to back it up.

As for the high mileage oil, it's about the same cost as normal oil. It's treated to stay thicker under more conditions (So a 10W-30 would try and stay at 30 weight under more temperatures), and is also higher in zinc content (Which is supposed to aid in valvetrain longevity). I haven't heard any complaints about it yet, but I also can't verify if it works.

Romeo wrote: As for the high mileage oil... It's treated to stay thicker under more conditions (So a 10W-30 would try and stay at 30 weight under more temperatures), and is also higher in zinc content...

Gotta link for any of that?

This is from Castrol's website, but effectively the three main differences between High-Mileage and standard oils are:

• A custom blend of polymers to better seal against leaks, especially under colder temperatures (The polymers added to the oils are what determine the weights, as well as their behavior).
• A rubber reconditioner, which inflates or 'baloons' seals, hopefully getting them to re-seal better.
• And 'metal additives' (This would be the zinc compound the AMS employee mentioned, I assume) to better coat and protect wearing items.

It is the same weight, but a polymer that expands with a lower thermal energy will thicken to it's 30 weight faster than one with a high thermal requirement, which will stay at 10 weight longer.

As for the article, I find that dubious, given that AMS (which isn't the most expensive oil on the planet) was the one that told me their high mileage uses ZDDP. As for Castrol, I'm not sure what it is they have, but presumably it would be something that accomplishes the same thing, if it isn't ZDDP in reality.