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Discussion Starter · #1 ·
What type of oil can I use in my Merc 350 smallblock?

when I last changed it, I used the Quicksilver brand stuff from a boat store... of course recommended by Mercruiser.

can't I just use a 40 weight oil? I think the manual said something about 10W-40 as a substitute.. I could only find 5W-40 at the store.
 
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I only use merc recommended oils and lubes. Quicksilver is actually Mercury. Just a different label. Or something like that.
I put only Murcury 25W-40 in my 502. That's what the book says, that's what I do.

Marine engines are so exact and precise, and the manufactures are so specific on what to use and not to use, I only only use what they say. Just my opinion/policy.
 

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I have used Valveoline (sp?) Racing 40w oil in my 350"s for the last 15yrs or so and never had any problems. The owners manual suggest 40W (for our temp range) or 25w - 40w merc.
Murrys or Kmart usually has the val 40w oil. Hope this helps.
 

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Discussion Starter · #7 ·
thanks. I was just reading up on what the oil classifications mean... and comparing it to what my Mercruiser manual says. It says CD or SG API classification straight weight oil.

Multiviscosity 20W-40 and 20W-50 are only when straight weight oil is not available. so I want plain ole 40W.

I'm assuming I can save a few $$ by not purchasing Quicksilver stuff.
 

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Be good to your eng. Its best long term to go with the mfg's recommendations ( sort of like wanting your car eng to last 150,000 miles or more).
The API ( American Petroleum Institute ) is sort of like the UL labs for electricity , they set the standards for lubricants .
Viscosity is the lubricants resistance to flow , therefore , the higher the viscosity , the higher the resistance . Where the eng most "feels " this is starting & warm up . The main diff in oils is the additives & refinery processes . High viscosity ( or cheap ) oil can turn to syrup ( great speller , eh ? ) when cold & makes the eng work harder . Impurities in the oil will create more friction ( therefore more heat ) on all the moving parts , & long term , the longevity of the eng.
You can get away with using a single viscosity , but multi-viscosity is better .
I use Merc 25w-40 . Its about $2.95 a quart , but its cheap insurance . You get what u pay for .
Likwise , you can use cheap filters , but again , you'd just be cheating your eng. There ARE differences in filtering properties , and god forbid , their ability to bypass in the rare instance they become clogged ( dirty oil is better than NO oil ) I use the Merc filters . They are about 6-7 bucks , so the price isnt bad at all .
I'm retired , so $$$ is def a factor , but i'll jus gather a few more pop cans if i have to.
Trust me on this one , I worked on jets ( engines ) for 34 years..............hope this helps....
 
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