Oil for a 4.3l V6 omc 1987

[Ianlinares]

Quick question. I read somewhere that I should use sae 30 for my engine, is that correct? For gear oil use sae 90?

 

[wrench 3]

OMC did recommend SAE30. However mercruiser runs the exact same engine on 25W40. The rep for my oil supplier said to use 15W40, but that could be because they don't market a 25W40.
So it's up to you.

 

[Ianlinares]

Thank you

 

[jerryjerry05]

I use 10-30 in the colder climate and 10-40 down south.
​Checked my manual it said 30 for the motor.
80/90 for the drive. Just make sure the drive oil is added in the right spot??????
​

 

[HT32BSX115]

Quick question. I read somewhere that I should use sae 30 for my engine, is that correct? For gear oil use sae 90?

Howdy,

Quick questions here about oil usually result in LONG answers about "what I use"

If you do not want to use what the manufacturer suggests, you can use pretty much any type of oil.........And all have been tried with satisfactory results.

The best choice would be any NMMA FC-W approved oil..........OR any other type oil. Just about everything has been tried with acceptable results.

For gear oil, no marine gear oil specification exists, so you can use any GL-5 (NON-limited slip) gear oil.

Most of us like synthetic 75W-90type gear oils.

Regards,


Rick

 

[Lou C]

Thete has always been much debate on this point. The idea of recommending higher Vis oils such as straight 30 or 40 and Mercs recommendation of 25/40 was based on the fact that lightet vis oils used in auto applications can shear down in high rpm use that you see in marine use. One way you can check if the oil you are using is good enough is to do an oil analysis with Blackstone Labs or similar. This will tell you what the viscosity is after a full season and also how the engine is holding up in general. The other test you can do is to check your hot oil pressure reading at idle after running on plane. It should be at least 20 psi, if not the oil may be thinning out.

 

[Lou C]

I have used straight 30,40 and the Merc 25/40. All have held up well. I have never used 15/40 but many have. Personally I would not use any auto based 5/30 oils in a marine engine. Remember you are cruising at an average of 3500 rpm which is rarely seen in auto use. The only time I ever saw that was when my cousin had a 'worked' '69 Chevelle SS 396 set up for drag racing with 4.10 gears and an M22 4 speed.

 

[wrench 3]

I have used straight 30,40 and the Merc 25/40. All have held up well. I have never used 15/40 but many have. Personally I would not use any auto based 5/30 oils in a marine engine. Remember you are cruising at an average of 3500 rpm which is rarely seen in auto use. The only time I ever saw that was when my cousin had a 'worked' '69 Chevelle SS 396 set up for drag racing with 4.10 gears and an M22 4 speed.

Not to mention that pretty well all marine small blocks don't run oil coolers, and there's not much air flow cooling the oil pan.