It appears that some on this thread either don't plan on keeping their boats long, or haven't considered the cost of rebuilding a marine engine. Amsoil published an article a while back about what Mercury racing discovered when they tore down Bob Teagues engines after a season of racing using Amsoil. In Mercury's own words, "No measurable amount of wear". I started my first business 40 years ago rebuilding engines and doing major engine repair. I have payed very close attention to the performance of many different types and grades of oil on an engine. I'm the type of person that doesn't even think about selling a vehicle until it has over 200,000 miles on it. The last vehicle I sold had run Amsoil from 60,000 miles and I ran a compression check at 225,000 just to see how it was doing. Every cylinder was within 1.5 lbs and they were all at factory spec. Now this was my work truck that I used and abused, I had overloaded at times so bad the tires were almost flat, I drove it like I stole it. I hit the redline every time I take off and at 225,000 miles no detectable deterioration. My current Suburban has 255,000 miles and it runs better now than when it was new. I have had several hot rods with full instrumentation and I have been able to watch non-synthetics start to break down at 500 miles. I currently change my oil every 10,000 because of the severe use, but at 10,000 miles the oil is still maintaining it's original properties. I've done the math and it is cheaper for me to run Amsoil than any other product. If you count the cost only by the price of a quart of oil you will be wasting a lot of money. Why do you think so many trucking companies are switching to Amsoil, they are looking to save money. There have been countless articles about trucking companies that have had problems with sludge or wear that were solved by switching to Amsoil. There is enough data out there to prove that at the very least Amsoil is one of the premier products on the market. I just paid $12,000 to rebuild my engine, I wouldn't run anything other than Amsoil if it were free. JMHO

same here

I hope people pay attention to the information in your post . +1 on the Amsoil .