5w40 diesel oil in outboard?

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I know lots of folks run 15w40 in outboard but I use my boat all winter long and was thinking 5w would be better. Would it be better to drain and go back with 15w in the summer? Or just run the 5w year round? I run 5w40 in my jeep and in my son's car so I usually have some laying around.
 
many people run 5W-40 (especially Rotella T6) in MANY thing "Not Diesel"

The Turbo Subaru uses T6 5W-40 almost exclusively.
 
I have Delvac 1 5w40 in 2010 5.3L ... Walmart had it for $23 a few months back … tipped my buddy and he snagged 45 gallons for his diesel and gas motors …
I’d run it in a boat … but have some Quicksilver stash on deck …

It is on roll back for $25 now
 
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Originally Posted By: Sealbilly
I know lots of folks run 15w40 in outboard but I use my boat all winter long and was thinking 5w would be better. Would it be better to drain and go back with 15w in the summer? Or just run the 5w year round? I run 5w40 in my jeep and in my son's car so I usually have some laying around.


How low of a temperature are you thinking of? A 5W can go to -30 c but the lake would be frozen.
smile.gif
A 15w40 is still good for starts to - 20 C.

I think you might be overthinking it, but if you want to baby the engine a 10-40 might be a good compromise. What does the owners manual ask for?
 
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Originally Posted By: Snagglefoot
Originally Posted By: Sealbilly
I know lots of folks run 15w40 in outboard but I use my boat all winter long and was thinking 5w would be better. Would it be better to drain and go back with 15w in the summer? Or just run the 5w year round? I run 5w40 in my jeep and in my son's car so I usually have some laying around.


How low of a temperature are you thinking of? A 5W can go to -30 c but the lake would be frozen.
smile.gif
A 15w40 is still good for starts to - 20 C.

I think you might be overthinking it, but if you want to baby the engine a 10-40 might be a good compromise. What does the owners manual ask for?


It calls for 5w30-20w40. With 10w30 being the "good anytime" recommendation. I usually have T6 or delo 5w40 on hand.
 
Yannick— what year? The requirement is recent. Although I’m not 100% of the exact year, most after 2014 do. I think California was the first to require them in sterndrives and inboards around 2008.
 
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