the only difference in motor oil formulation is the type of engine, as far as the oil is concerned there's no difference in a marine gasoline engine (inboard or outboard) and the engine in your car, they run at similar rpms and temperatures. and before anyone says anything about loading differences you need to go read any of the good in depth studies that can be found using google about viscosity (how the oil protects the engine) retention traits in oils at different temperatures, rpm, age, and particulate saturation. the only time getting a different oil is important are cases like i referenced at first, motorcycles with wet clutches need specific types of oil to handle the particulates from the clutch and keep the plates from glazing and often (japanese 4 cyl bikes) handle rpm figures well in excess of 10,000 for long periods, two strokes need to handle high rpm and also be able to precipitate onto the cylinder and crank case walls after being carried into the engine with the fuel from the carb. the four stroke gasoline engines we have in marine applications pretty much only differ from our cars in the cooling system, the oil system runs at similar pressures, with similar pumps, at similar rpms, at similar temperatures.
having said all that i will submit this study.
http://www.mr2.com/ARTICLE/Mobil1.html
and this one.
http://www.2002tii.org/kb/288
same test i know and not as much info as ive found in the past about the oil itself but seriously guys 1 million...MILLION miles and the connecting rod bearings measured .0008 wear from factory spec.
the guy at WM is going to want you to buy his oil, go to his mechanic when the motor breaks, then accept that its "just part of owning a boat" and keep buying his oil.
here is the study i found a few years ago, i had just paid my own savings at 19 to have the ford 302 in my 1988 grand marquis rebuilt and was determined to make my investment last (silly me i didnt keep the car for more than 3 years after that) regardless my youth and vigor drove me to find out some real world info on what oil i should use and this is where i ended up after comparing to the often lauded but dismal results of all the other oils i could find in my local stores
http://www.brianschreurs.org/neptune.spacebears.com/cars/stories/mobil1.html
lol sorry for the rant guys, i just noticed the op got that list, i noticed motul brand oil on there a few times, those guys know oil...they've got the best products for motorcycles by far, used them in my dirt bike (125cc two stroke making 37hp) and my street bike (yamaha r6)
