Oil question again

Why did my new GYTR head come with yamalude syn oil?  Marketing deal? I use reg yamalube oil already and been very pleased. Motor has 105 hours on original parts. Piston and rings like new. Just wanted a little more and got excellent deal on NEW GYTR stuff

What is it exactly that you want to find out?

Is it really better to use at twice the price?

How long do you go between oil changes?

Every weekend we ride. Practice 4 sessions sat and 4 motos sunday.

Then it may not be worth the expense.  If you change on that basis, most oils that show up to date API gradings will work OK, particularly if they are marked for commercial truck use (API grade "C*").  A top tier synthetic will protect your engine better, but under "most 'normal' conditions", it's not going to be twice as good.

 

Where the problem is with motorcycles is that most of them share the engine oil with the transmission.  Multi grade engine oils are made by adding compounds that get bulky when hot to the thin base stocks used.  A 10w-40 is a 10 weight oil made to be no thinner than a hot 40 weight when it's at 200 ℉.  The shearing pressure that the transmission puts on these additives can physically shred them, and then, of course, they don't work anymore, which leaves you with a 10w-25 or something when you thought you had a 40 working for you.  

 

Oil blenders can use tougher versions of the additives, and have done so for years in blending multi-vis gear oils that are expected to serve for thousands of miles in truck transmissions and axles.  The additives cost more, though, and most car oils use the less expensive ones.  These days, I would estimate that 75% of "car oils", maybe 40% of "Commercial/Truck/SUV" oils, and about 35% of "Motorcycle" oils at any price point will fail to stay in their listed viscosity grade for more than two hours when used in a raced YZF.   But since you are changing that frequently, shear stability shouldn't be too big a concern. 

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