The question based on the numbers is tee’d up like a softball, so I am going to hit it... Are you satisfied with the oil shearing out of grade to barely a 30 wt? I gather shift quality stays good, as that would seem to indicate shift quality going down with that amount of shear/reduction in viscosity. With the 5,200 mile OCI, it is barely 30 wt with a flashpoint of 415. Nice to see it hasn’t dropped much lower as you have extended the oil change interval each time and based upon the second and third OCI’s having a much lower flashpoint. I share each time I see really low retained viscosity that M1 10w40 4T and M1 20w50 V-Twin stay in grade in my shared sump ZRX 1200 for 5,000+ mile OCI’s. Even if Castrol 10w50 is lower priced, which I don’t believe it is, something that stays in grade may be worth considering?
I say this tongue and cheek, but maybe just start with a 30 wt like BLS has been promoting all these years...
No, they didn't mention what the average interval is but I am guessing it is much less than 10K.
Historically I have changed around 3K to 5K because of sheering and notchy shifting. When I changed out the 4 quarts one of the thing I was looking at was how much the shifting would change and it surprised me that I didn't notice much difference. I have ran some oils like Rotella T6 in the past where I really felt the gearbox degrade. This oil didn't.
I chose this oil because originally I got a really good deal on it and so I ordered a few cases. No belief in any special magic of the Castrol.
I really don't know as I care if the oil is shearing down. The metals dropped so it can't be hurting the engine, the shifting had almost no change over the life of the oil (shifts great).