Not meaning to hijack this thread, but it evolved into a discussion about lubricants. Below is the Mercury link that discusses fuels and lubricants.
One item of importance in the oil section is a note saying not to use oils with solids in them. I know of one highly rated synthetic, special order in most places, that has molybdenum as an additive. Moly is an excellent lubricant but it is a solid and can "break out" of suspension under certain circumstances.
I have a new truck that I am running synthetic in and I chose a different brand that didn't have moly in it. Still special order, though.
http://www.mercurymarine.com/fueloil...mendation_faqs