10w-30 or 25w-40 oil for 150 pro xs

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My manual for my 2018 mercury 150 pro xs 4 stroke recommends 10w-30 for general use but says I can use 25w-40 synthetic blend oil too. What are the advantages of each of these oils? I never go out unless it’s 50 plus degrees out and it rarely gets over 85 where I fish. Will the 25w-40 protect the engine better? Interestingly the manual specifically states not to use full synthetic oil.
 
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Texcl2

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Texcl2

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My post above is the oil recommendation. I have to worry about my warranty as it is still good for three years at this point. I don’t think heavy duty 30 weight will work with the warranty.
 
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"10w-30 may be used if temperatures are below 0C or less" is pretty clear that in your conditions it should always be the 25w-40.
 

Texcl2

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Sorry guys I cut off the first half of the manuals oil recommendation........

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Texcl2

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My outboard is a 150 pro xs not a sea pro.

it’s seems both are fine but are there advantages to the 10w-30 since it’s thinner? Like at start up? I’m more worried about engine life vs fuel economy so if the 25w-40 protects better but gives up fuel economy I’m ok with that.
 
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My outboard is a 150 pro xs not a sea pro.

it’s seems both are fine but are there advantages to the 10w-30 since it’s thinner? Like at start up? I’m more worried about engine life vs fuel economy so if the 25w-40 protects better but gives up fuel economy I’m ok with that.
I think that you just answered your own question. Nowadays any decent group II SAE 40 will pass 25W.
 
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My outboard is a 150 pro xs not a sea pro.

it’s seems both are fine but are there advantages to the 10w-30 since it’s thinner? Like at start up? I’m more worried about engine life vs fuel economy so if the 25w-40 protects better but gives up fuel economy I’m ok with that.
"Protection" does not come from the winter rating. Ease of starting does but not any sort of protection. Any oil when cool or cold is overly thick and provides a sufficient MOFT for protection.
 

Texcl2

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that’s what I was thinking but figured I’d ask in case there was something I was missing.

I’m suspicious that the 10w-30 recommendation is an emissions/fuel economy thing at the cost of engine life.
 
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that’s what I was thinking but figured I’d ask in case there was something I was missing.

I’m suspicious that the 10w-30 recommendation is an emissions/fuel economy thing at the cost of engine life.
Or they have determined that a 30-grade oil has a high enough HT/HS and provides sufficient MOFT. it's not always a conspiracy :)
 
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SeaPro is Mercury's commercial line. These engines are expected to be worked hard. Mercury recommends the 25w40 for them, with the 10w30 as a substitute. I

f it was me, I would run the 25w40, as I am confident that there are no differences in the long block between the SeaPro and the ProXS models.
 

Texcl2

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I was wondering what the difference was, thanks for the comment.

I might send an email to mercury to see what they say about it.

I’m a maintenance freak, I think I like learning about and working on my stuff as much as I like using it. I kept my old Toyota Corolla just to see if I could make it to 300k while my wife was driving her new $60k suv, think she was secretly happy when my son wrecked the Toyota at 270k miles, lol. That car ran like new because I always maintained it and used synthetic oil in it. My f250 has over 250k miles and going strong. I finally broke down and bought a new Titan to pull the new boat because my wife claimed she was worried the f250 would break down on us some day out in the middle of nowhere. Anyways, I’m hoping I can make this outboard last forever, seems consistent maintenance and good fluids are the trick.
 
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If you do send the email, please share it here, if you don't mind. I would love to hear what they have to say.

From my limited knowledge of the Merc 150, and from what I've heard in chatter around the dock, is that it is a very stout platform. A friend of mine knows someone running a SeaPro 150 in a commercial application, used almost daily. 2500+ hrs and going strong, with minimal downtime.

Sorry if I missed it, but what are you running your ProXS on?
 
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My manual for my 2018 mercury 150 pro xs 4 stroke recommends 10w-30 for general use but says I can use 25w-40 synthetic blend oil too. What are the advantages of each of these oils? I never go out unless it’s 50 plus degrees out and it rarely gets over 85 where I fish. Will the 25w-40 protect the engine better? Interestingly the manual specifically states not to use full synthetic oil.
Quicksilver oils are designed with Mercury motors in mind.
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