Re: Oil Viscocity for 1993 OMC 5.0 (Ford)
Owner's manual oil recommendations are completely irrelevant, especially when it was written in 1993 and it is 10+ years later. Many things have changed.<br /><br />Go with a 40 weight oil, straight 40 if available is ok unless you boat in weather < 60F in which case a multi-viscosity like 15w-40, 25w-40, or 10w-40 would be better.<br />Chevron delo 15w-40 or mobil delvac 15w-40 I think would be your best bet, should be available at any auto store including marine stores like west marine but you'll pay more there. A 10w-30 won't hurt, but might give you lower oil pressure at hot idle.<br /><br />Here's a quick fyi on oil- today's oil is driven by the automotive market and the EPA and gov't pressure for fuel economy. There are formulated thinner to give better fuel economy and with less additives to reduce emissions and lengthen catalytic converter life. Proof of this is all the 5w-20 and 0w-20 oils you see on shelves and specified by new cars- ford/mazda, chrylser, honda. Not the greatest thing for a boat engine which is under a much heavier load all the time. This is the main reason you are unable to find straight 30 oils- not fuel efficient according to your gov't and the epa and they don't sell. Stick with diesel-rated oils if possible, will have a CH-4/CI-4+ rating on them in addition to SL or SM, they will offer the most protection unless you go with a boutique or name brand synthetic. Pennzoil 15w-40 is also usually available at places like walmart. Otherwise 10w-40 valvoline, havoline, mobil will all do just fine. Multi-visc oils are not bad for the simple reason technology and oil refining is much better today than it was back in the early 90's and 80's. They will not shear/oxidize/break down, or at least are much much less likely to. Opinions die hard which is why so many can't offer any helpful advice regarding lubrication.
