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Thanks...Will let you know when I get it home, and what it needs. 10W - 30..that's what I use in other vehicles. What about synthetic, I've heard not to use synthetic in older engines, as it may make the seal leak.
 

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Synthetic

I would recommend Mobil 1 10W30 or 5W30. I use the 5W30 in my GT. Mobil synthetics are made from PAO's (poly alpha olefins). They simulate Parophinic petroleum base stocks but are superior because they have better temperature stability. ( Can handle high temperatures for extended periods of time with out breaking down) Because PAO's simulate petroleum base stocks, they will not attack seals or gaskets. The stories of synthetics attacking seals came from the use of esters and diester base stocks. I'm not sure whether any of the major suppliers of syntetics still use esters & diesters. Until recently all suppliers of PAO syntetic motor oils purchased their base stocks from Mobil. There are a lot of "Mom & Pop brands" out there, but I prefer to stay with Mobil. They pioneered synthetic motor oils and have more knowledge and experience than all of the others combined.
 

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70's Opeler, back 4 more!
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The issue I understand with using Synthetic in older engines is not that they attack the seals, but that they clean all the junk away from them, thus causing them to leak. Synthetics have more detergent in them than dino oils, which acts to clean all the "junk" that builds up in an engine and around the seals. Seems the molecular structure of synthetics also allows it to find smaller holes to seep out than dino oil.

Any way, after a while, synthetics can also reseal the same leaks they opened up.

Also, once you go Synthetic, Stay synthetic. I also understand that it is NOT a good idea to swap back, again, due to the impurities in dino oil.

You can do a search for this and check out the results. Looks like about a 5% chance of leaks.

I am currently running synthetic in my GT. I switched over about a year ago. I changed oil and ran that for about a week before changing it again to remove some of the junk cleaned out. I then ran that for the next month and, again, changed it. I did experience some leakage, but the leak is slowly subsiding (either that, or there's less oil in it now. :eek: )

Oh yeah, and I knew the engine had been overhauled not too long in the past.
 

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Synthetic?

Synthetic oils are not naturally higher detergency. This is mostly dependent on the additive package. In actuality Synthetics are usually lower on detergent qualities because the natural of the base stock, (having less variety of molecular chains), makes it more difficult to hold additives in suspension. For this reason Mobil puts just a touch of diester in their Mobil 1 oil for additive retention. The old stories about switching between synthetic and petroleum products is based on incompatibility between synthetics made from esters, diesters, and glycols. PAO's do not have that problem. You could think of PAO's as simply a purer form of a parafinic based petroleum oil. By the way all petroleum based oils can be classified in terms of the percentage of parafinic and aromatic in the base stocks. Parafinic has better oxidation stability, (high temperature stability) and aromatics have better natural detergency.
 

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Just a note from the Moderator guy. I split the previous thread with bozkm's introduction, as this was heading down a different (and interesting) path.
 
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