I have been using and selling synthetic oil for over 26 years and have never had a problem in my own collection of engines, (which include everything from single cylinder stationary engines from the 30's to 450+ hp engines from the 60's ), or in any of my customers engines or transmissions, and I have sold thousands of oil changes. There are some simple guidelines on when to use synthetic oils, and if they are followed they are superior to any standard petroleum oil in every way. Firstly, you can't save a sick engine with synthetic oil. You should never use synthetic oil as a break in oil because the rings will not seat because there isn't enough friction. If you don't have a filter on the engine, you should not increase the oil change interval. There are many more, but I have just been called away. I flew fighters and commercial jets for 40 years, and every one of them was serviced with synthetic oil because of its superior characteristics. On the big jets in the company I flew with, the oil was sampled every 100 hours ( approximately once a week ) and the oil could stay in the engine for a considerable period of time. The longest I am personally aware of was 26.000 hours without a change. The reason the oil was changed at that time was because of a hot section component failure that contaminated the oil. There are some synthetics that are better than others, and a major brand name doesn't mean that the oil is the best of the pack.
Bob
