[Robert]

Hi Eric, Sorry I’m a bit late to this topic. I’m not an expert, but I had asked a representative about the synthetic oils and some of the leak issues I had with them. This individual stopped by our shop at an Air Force base I was stationed at a back in the 80’s to talk to us maintenance folk about the new synthetics that started to get to us through supply. I was told that some unit had experienced some problems and someone was trying to blame the synthetic oil and some rumor’s were going around. At about that same time I had changed the oil in a 68 Camaro I had with the synthetic. I had rebuilt the engine a few years back and had mileage on it and I changed the oil at recommended intervals. But when I switched to the synthetic it started to leak, so I asked the Rep if the new oil had caused it. He told me that the non-synthetic oil I had been running in the car had built up some carbon around the seals that had dried out a bit and got hard. The synthetic oils are very high detergent and washed some of the carbon build up that had formed on some of the seals and had caused the now noticeable leaks.
What he told me was that if you had been running conventional oil in an engine for a long while, don’t use synthetic oils or the small unnoticeable leakage would become much larger. However if it was a fairly new engine or a rebuilt, go with the new synthetics, it keeps the new seals from drying out and getting hard. It keeps the engine wear down and the engine would be much cleaner with the regular oil changes. How much of that was BS or selling points for the synthetic oils, I really don’t know. But, I had rebuilt that engine and never had leaking problems for about 100K. Unfortunately my ex wrecked it. Every other car I’ve had since then I’ve run synthetic and have not had a leakage problem. I’m now of the opinion, that if someone wants to run the synthetic in an older car, that has been using conventional oil, my advice would be to tell them not to. But on a new rebuild or a new crate engine, synthetic oil is the way to go.
I hope this might help with the synthetic vs conventional oil. Synthetic is so much better for the seals and keeping engine wear down.

[Author]

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