Bill, This is great information. Thank You! I think it is clear to me that it would be better for my 2 cycle Yamaha 4 hp. to mix something less than 100:1. I am thinking I will go with 50 or 60:1. My next quest is to try and find a synthetic and bio-degradeable outboard oil locally in 1 quart containers. I have found it in 1 gal containers at West Marine, per Harvey's recommendation. I calculate 1 gallon would last me about 20 years! I am still curious about the Amsoil 2-cycle synthetic. They recommend their oil to be used in normal application at 100:1, and 50:1 for high heat and high demand racing applications. My father in law swore by Amsoil, he used it in everything he had for over 30 years. Randy Graves M-15 #407 -----Original Message----- From: Wcpritchett@aol.com [mailto:Wcpritchett@aol.com] Sent: Sat 5/17/2003 1:53 PM To: montgomery_boats@mailman.xmission.com Cc: Subject: Re: M_Boats: 2-Cycle Oil Recommendation For what its worth I will pass this info along. I got it from a friend of mine who used to be the head warranty mgr. for OMC International (commercial division outboards) for South America, Bahamas and Bermuda. He flew all over the place inspecting engines for 10 yrs...and is a BSME, PE and MBA. This is dated back to mid 90s just before OMC tanked. OMC only used 100:1 mix for a couple of years and went back to 50:1 because of corrosion problems. They found that people who let their engines sit for months between use were the ones having warranty work. 100:1 doesn't leave enough film on the internal parts to protect long storage. A 100:1 engine is identical to a 50:1 engine. A typical 80s/90s vintage OMC (evinrude/johnson) only needs 150:1 lube at full throttle and 300:1 at idle. There is a huge safety factor in the mfg. specs. He also said it didn't mater which brand you used as long as it was TWC rated. Concerning synthetic...there was no detection of better wear but was cleaner running...so you can go longer between decarbs. He said synthetic was not cost effective for the avg. boater but to use it if racing because it will turn faster. Synthetic does not cling well to internal parts so fogging is suggested for long term storage in humid climates. Here in Florida that means 2 months. Bill