Originally Posted By: bonjo
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BTW did you say bike you are running
This is the big question.
An air cooled bike has different needs than a water cooled bike.
A big, low revving v-twin cruiser (air or water cooled) will be different than a high revving sport bike.
Also riding style and OCI play into it.
A synthetic will tend to have less breakdown than conventional.
A straight weight will have minimal breakdown.
Oils with a smaller viscosity spread also hold up better.
Every bike also can have issues with specific brands, especially if a shared sump wet clutch.
While I currently have Peak Syn-blend 15w-40 oil in my bike and it works great for me, someone else can use it and have issues. I have also used Supertech 15w-40 and had no issues, but again, others have on their bikes when using it.
That is why comparing bikes like yours is important.
15w-40 is fine for most water cooled bikes.
20w-50 for most air cooled bikes.
Yes these are generalizations, but without more info, it is hard to say.