Synthetic crank oil yes or no? Tohatsu 20 4s

Joined
Aug 15, 2008
Messages
8
Was going to do the first oil change in my 20hp 4 stroke as well as the leg oil. Ill be using amsoil 75-90 syn in the leg, but I have read not to use synthetic for the crankcase. Is this true?

I have used amsoil previously in my yammy 9.9 without any probs. Should I go with a thinner weight than 10w30? I live in Calgary and the motor will likely never be used in temps above 85 degrees. Most temps will be in the 60-80 degree range.

Thx very much
 

DECK SWABBER 58

Lieutenant Commander
Joined
Aug 14, 2009
Messages
1,913
Re: Synthetic crank oil yes or no? Tohatsu 20 4s

I'm sure the same applies with the 20 as with my 9.8. These engines run on the cool side and tend to make oil. Synthetic makes it worse because it will run even cooler. I use non-synthetic FC-W 10-30 Quicksilver. Do a search on this forum and you will find a lot of info.
 

pvanv

Admiral
Joined
Apr 20, 2008
Messages
6,500
Re: Synthetic crank oil yes or no? Tohatsu 20 4s

Use non-synthetic FC-W 10-30.
 
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