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MerCruiser Oil

srdancer90

Regular Contributor
"I have a pair of 320 MPI MIE

"I have a pair of 320 MPI MIE Mercruiser engines. I will be winterizing the boat within a few weeks, and will be changing the oil for the lay up. I have read in the mercruiser man that I could use straight 40W oil. I recently spoke with a mercruiser rep on the phone and he stated that the use of a straight weight should be in an emergency only. The man states that it is dependent on the temp within the season. So here is the question Why the use of a 25W-40 when it states that a straight weight can be used? Also the Merc tech stated that there were special additives in the 25W - 40 that the straight 40W (other manufactures brands) do not have. Is ther any truth to this? If so I will use the 25W - 40."
 
[i]Why the use of a 25W-40 whe

Why the use of a 25W-40 when it states that a straight weight can be used?

because it only states that straight 40 can be used above 50 deg. F ambiant

My boating season would be about 3 weeks with that oil.
Where you live it might be fine.
 
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