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Oil Viscosity

CobraDave

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I’m planning for my next service and like to use Amsoil in all of my stuff. Amsoil only makes a synthetic blend in the recommended viscosity in my Mercruiser 2017 6.2 350 (25W-40).

They do offer two other full synthetic marine oils at 10W-30 and 10W-40. I was contemplating 10W-40 to get a fully synthetic oil. Am I better off switching brands? I’m sure the blend would be fine but I want the extra protection.


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mattyc

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The 10w-40 ought to work fine. It will flow easier at cooler temp
 

LargeOrangeFont

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Run the 10W40 Dave, it will be just fine.

I have ran the Amsoil 10W40, and Volvo synthetic 10W40 that is supposedly made by Amsoil. This year I switched to Mobil 1 15W50.
 

CobraDave

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Thanks maybe I will. Im curious why Amsoil makes the standard Merc weight a semi synthetic. Kinda odd.


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LazyLavey

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I'm gonna open this hole a little.. well, probably alot

I've been running Kendall straight 40w for 20 years, as recommended by Teague, in a basically 2000 454 mag, . No issues that I'm aware of except a very minor leak I believe from the front seal

At this point is there any benefit running multi weight? or synthetics ? or just leave it alone?
 

LargeOrangeFont

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I'm gonna open this hole a little.. well, probably alot

I've been running Kendall straight 40w for 20 years, as recommended by Teague, in a basically 2000 454 mag, . No issues that I'm aware of except a very minor leak I believe from the front seal

At this point is there any benefit running multi weight? or synthetics ? or just leave it alone?

It think that is perfectly fine. If it has been working, run it.

Up until a handful of years ago Volvo Penta recommended straight 30wt. Their engines were basically identical to Mercruiser engines with their oddball 25w40 oil specification (which is close to a straight 30wt anyway).

I don’t have many reservations about running a single weight or thicker multi weight in Havasu with the intense summer temps.

I noticed a slight increase in idle oil pressure at hot idle with the 15w50 Vs. the 10w40. Under load oil pressure seems about the same.
 
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CobraDave

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I do believe in getting a quality synthetic oil vs Dino oil. There is so much proof and research into the topic that proves the idea.

I don’t like to stray to far away from the oil weights recommended by the manufacturer. And it’s because I am not an engine builder or engineer so I’ll take their word over mine. With that said, they use a standard weight for most climates so I can see the reason to change it up for the Arizona desert. A straight 40 weight makes a lot of sense. Going from 25w40 to a 10w40 concerns me a little. I’m sure the viscosity gets to 40 pretty quick and isnt much different.


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