Is there a reason not to use the type of grease the manuals suggest? It's all I've ever used in wheel bearings and they've all lasted tens of thousands of miles...
For around 30 years I was using only Castrol Grease in the Wheel Bearings.
A while back, BP bought Castrol and I found a marked change in the Castrol lubricants since. I don't know if this is only local to us here in Aust or if it's world wide.
I've since gone to Timken Wheel Bearing Grease and found it streets apart from the Castrol. The Castrol I often found burnt after 6 000 miles where as the Timken is still fesh as the day it was put in.
That's interesting about Castrol. I used to use Castrol LM in the nineties but since coming back to Minis I've just used whatever Minispares have which seems to be Comma grease. I looked into Timken grease but it seemed like it would take a little digging to acquire some. Why it doesn't come with the bearings I don't know.