5W-50 or 15W-50 for 18HP Vanguard? Does it even matter?

[redhat]

My 18HP Vanguard V-Twin is getting a new home in Dad's 1984 John Deere 318 within the next week. The original Onan B43G is drinking a lot of oil, down on power and emitting large smoke plumes at times.

Trying to decide between 5W-50 or 15W-50 for the Vanguard. Reading through the Briggs owners manual and general consensus on here about air-cooled engines running with a decent load, it sounds like a xW-50 is not out of the question.

I keep Mobil 1 5W-50 FSX2 on-hand for my 2020 Sportsman. I would enjoy just using something off the shelf.

With having my 1025R, I don't use my 316 a lot anymore. I intend to put it aside and come back it in the future. Would rather see Dad use this motor than watch it sit. Has maybe 100 hours on it.

 

[DriveHard]

if it were mine, and only used in summer I would lean toward the 15w-50 for more shear stability.

 

[Invisible]

Unless you live at the North Pole, go with 15W-50 year-round.

 

[dnewton3]

... "Does it even matter?"

Given the choices you mentioned, it does not matter.

 

[Cujet]

15W-50, hands down.

The 5W-50 is not shear stable and is nowhere near as robust.

Despite the changes to the M1, 15W-50, it remains a superb oil, remains thin when cold, has a high HTHS, provides superb cleanliness and is very shear stable. In my opinion, there has never been a better air cooled OPE engine oil.

 

[Rand]

I like 15w40 in air cooled ope engines but out of those 2 choices
15w50 if not used in winter conditions.
My 316 onan currently has motul 300v 5w40 in it.(out of the metal 2L can)
anyone else going to shed a tear when I dump it at 40-50 hours.

Just had nothing left to use it in and a few random cans. (next up 0w40 metal can motul)

 

[redhat]

15W-50, hands down.

The 5W-50 is not shear stable and is nowhere near as robust.

Despite the changes to the M1, 15W-50, it remains a superb oil, remains thin when cold, has a high HTHS, provides superb cleanliness and is very shear stable. In my opinion, there has never been a better air cooled OPE engine oil.

Thanks @Cujet I recall you mentioning this on I think it was my free generator post. I can recognize that on non-liquid cooled OPE, you can really work that oil and this is what I want a robust product for. On liquid cooled atvs, tractor, etc, different story.