1987 3.0 GM engine oil

[Starcraft5834]

With help of several, I believe I have successfully winterized my boat.. pulled plug on block and manifold, used my air compressor to blow it out to make sure,, all water is out...changed out drive oil and engine oil.....

Manual for my 1987 3.0 GM said to use Merc Oil, or a good 20-40W or 20-50 W.. I put 20-50 in it today,, new filter,,the oil cap on top of engine says 10-30W?? what's up with that? Considering the age of my engine, would think the 20-50 would be a better call... what do you guys think,, 10-30,,20-40, 20-50?

 

[HT32BSX115]

Re: 1987 3.0 GM engine oil

what do you guys think,, 10-30,,20-40, 20-50?

Oh boy......here we go.......

What type of oil should I use? Can I use synthetic oil?

Engine Oil
For optimum engine performance and maximum protection, use the following oil:

Application	Recommended Oil
All MerCruiser engines	Mercury MerCruiser Full-Synthetic Engine Oil, 20W-40, NMMC FC-W rated

IMPORTANT: Lubrication requirements for catalyzed engines differ from the requirements for non-catalyzed engines. Some marine-grade lubricants contain high levels of phosphorus, which can damage the catalyst system on MerCruiser engines. Although these high-phosphorus lubricants may allow acceptable engine performance, exposure over time will damage the catalyst. Catalysts damaged by lubricants containing high levels of phosphorus may not be covered by the MerCruiser Limited Warranty.
If Mercury MerCruiser Full-Synthetic, 20W-40 oils is unavailable, use the following lubricants, listed in order of recommendation. If you are servicing a catalyst engine, use these for short periods of time only.

1. Mercury/Quicksilver 25W-40 Synthetic Blend, NMMA FC-W-rated 4-cycle MerCruiser oil
2. Mercury/Quicksilver 25W-40, NMMA FC-W-rated 4-cycle MerCruiser oil
3. Other recognized brands of NMMA FC-W-rated 4-cycle oils
4. A good-grade, straight-weight detergent automotive oil according to the last row of the operating chart below.

NOTE: We do not recommend non-detergent oils, multi-viscosity oils (other than as specified), non-FC-W-rated synthetic oils, low-quality oils, or oils that contain solid additives.

This crankcase oil recommendation supersedes all previously printed crankcase oil recommendations for MerCruiser gasoline engines. The reason for this change is to include the newer engine oils that are now available in the recommendation.
Older Operation, Maintenance & Warranty manuals, Service manuals and other publications that are not regularly updated will not be revised to show this latest engine oil recommendation. Current Operation, Maintenance & Warranty manuals, Service manuals and other service publications that receive regular updates will receive this revised recommendation the next time they are updated.

You can do a search for "what oil should I use" and you'll get as many answers as there are people blogging here.

If you don't want to use the oil suggested by Mercury, you can use whatever you want. It's all been tried. (successfully)

 

[Starcraft5834]

Re: 1987 3.0 GM engine oil

Admiral....lol,, thanks,,,,as long as I dont use Corn Oil. Im probably good.......