In gas engines I have had a lot more engine "issues" with synthetic oils than dyno oils but I have never had an oil related failure using either type. We are on our second BMW M3. The first came from the factory with dyno oil and the second, with the same identical engine, came with synthetic, and still runs it, though I really despise it at this point. The synthetic engine has had THOUSANDS of dollars of oil leaks fixed in 130k miles. while the dyno motor had zero leaks over her life and when we sold the car with 140k she was still leak free. Both engines were spotless inside and the compression in both was spot on. I really have a hard time seeing a real benefit of synthetic oils in the short mileage we run cars in the US.

My brother-in-law commutes from NH t to MA every day, about 214 miles/day. His 94 Accord has over 700k on it,. It has had oil changes roughly every 7k with el-cheapo dyno oils. The engine & transmission are still 100% original and never re-built. Most people will NEVER, EVER run a car for 700+k yet I know the cheapest dyno oil on the market can help a Honda Accord go 700+k..... Rust is killing his car more than engine or trans mission failures and I think she'll be dead by next year. He has said he wants to do 1 million but I don't see it happening cause of the rust..

This was the top end of my Westerbeke 44B Four at 2878 engine hours just after I removed the valve cover. I have no doubt that the Rotella 15W-40 has been doing a good job at keeping my engine chugging along, and keeping it quite clean to boot. Oil analysis has also come back very good over the life of this motor. I change it every 40-50 hours cause it's cheap & easy and engines are $$$$$. 50 hours Overkill? Probably, but I like what I see when I go inside the engine...;)