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What grade oil to use?

B

Beany_bot

Member
Hi, sorry, I would check the manual but the boat didnt come with one. I've had a google but a lot of conflicting information out there.
Simple question really. What grade oil do I need for my 1991 5.7 V8 OMC engine?

Thanks
 
30WT is what OMC manual calls for.
Some use 20W50, or 25W40, which are very similar viscosity, if they have a hard time finding straight 30.
 
I'll try my best to find it but I might struggle here in the UK. Should definitely be able to get 25/40.
Would this be mineral, semi or full I should get?

Thanks
 
sure. That looks fine.

You know every lawn mower engine pretty much calls for straight 30. So if you have grass in the UK, you shouldn't have too much trouble finding 30WT anywhere lawn mowers are sold.

mineral oil fine - that's all OMC ever used.
If you boat in cold weather, with temps below 50F, you may want to go to a 20W50, or even a 15W40 if freezing temps.
 
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