Re: omc 5.8 1989 oil change best oil to use?
Hi ther talies13, this always seems to be an ongoing topic. MY general rule of thumb nowadays is..."EFFICIENCY, EFFICIENCY, EFFICIENCY". Most people and columnists say follow mfg's recomendations and most marina operators and mechanics say use conventional straight 30w. I use and suggest using a Synthetic oil and go with 10w-30 of a good known quality brand as these oils provide the best protection in all weather temps, control sludge and eliminate sludge as well as carbon build up in chambers (part where valves and spark plug is) AND is best choice for EFFICIENCY. When you can provide ANY sort of efficiency to ANY engine, your get two free components..... better gas mileage AND horsepower. Dont let ANYBODY tell you to not to use it....they're simply not informed yet on synthetics or are just not sold on it and are just plain stubborn. Remember one important thing here. All gas boat engines are not built by boat mfg's. They are engines that are made by either GM, Ford or Chrysler and are "crate" engines and are shipped out to boat building factories. (speeking mostly of v-8 and v-6 eng.) You didn't mention what type of engine you have so im gonna guess its a v-8 or v-6 so you're good to go if its one of these or even a 4 cyl. Diesels are different im sure. Most V-8 engines from GM and Ford are considered and built as replacement "truck" engines that work harder but can still benefit from synthetic oils. Its my opinion that conventional oils will soon be gone exept for a small quanity and few select grades. Maybe one exception here with your boat being run in a very warm climate and the possibility of your eng running strong and for extended periods of time running on the water would be to stick with conventional 30W oil, and change it half way thru the season. ALSO... if your temp gauge seems to indicate that its running a little on the warm or hot side, then also stick with conventional 30W. If temp gauge reads around 160 degrees or less, then I say use synthetic 10W-30 for best protection against sludge and carbon build-up. Most boat engines have 160 deg. thermostats. Sometimes they have cooler stats. I'v read where boat engines (V6,V8s) really need a stat of 190 or 195. This means that the eng will run better because its burning the fuel mixture more complete and thus it becomes more efficient. Theres that word "efficient" again! If ANY engine runs too cool, it will develope more carbon. AND carbon is or can be a real problem that gets misdiagnosed all the time. Run a Fuel Injection Cleaner now and then to help burn (or melt) off carbon from the chambers and hidden side of valves! Also run some Marvel Mystery Oil in fuel tank at times to further burn off carbon. Put it in engine oil and idle it for 20-30 minutes just before oil and filter change to help melt off or clean sludge/carbon from valve guides and valve stems too. Doing all this will ensure a quiet and smooth running engine and it will also be more EFFICIENT. I hope all this helps! IMO, it helps to have a "leg up" on competition when it comes to having an engine that runs better and is more efficient than the next boater with the same size engine, don't you think? It works for me! My 1994 Chevy pick-up has 305,000 miles on it and still gets 19.5 mpg's highway and it DOES have the origanal 5.0 ltr. motor in it! With a 205 degree stat in it too! EFFICIENCY is the new word of the decade. Have fun with it.
