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Old 07-05-2021, 10:15 AM   #1
bigdog
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Default Oil type viscosity / Regular or Synthetic ?

I will be changing my oil & filter in my 2000 4.3L Mercuiser V6 this week.

I don't have an owner's manual, but what I have been able to research the manufacturer recommends 20Wx40 Synthetic oil.

I am the second owner, and the original owner always used conventional straight 10Wx40.

Questions:
1) Is there a major difference between 10W and 20W viscosity ?
2) Is there an advantage using 20W oil ?
3) Conventional oil vs Synthetic ? Is there a real advantage ? I know conventional oil contains carbon, which can leave deposits on valves and pistons, which can shorten life, but using in a boat where one only puts few hours use per year, would 'Syn' really make any difference ?
4) Thoughts regarding 'synthetic blend' oil ?

Feedback appreciated....

Thanks !
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