Shifter cone in 280

Good morning, Yesterday when I was buying some seals, etc. for the old 280 I am maintaining, one of the clerks mentioned something which I would verified. He said if the cone has been updated, then heavy or hypoid oil is used, not engine oil. When I drained the oil out came lots of water and hypoid oil. Thus my examination of the seals etc.
But before I reassemble I would like to know if his comment is correct. And if so, is there an ‘easy’ way to verify that the cone has been updated? Many thanks for your thoughts! I have gleaned a lot of good info from this site. John

My understanding of the hypoid vs engine oil has to do with the manner in which oil is 'circulated' in the drive
. This is question best resolved by those more expert on these drives than I am.

You shouldn't use the heavy oil in a drive that has an oil pump on the forward gear. The old clutch's don't care. The new (290 and newer) clutch's only like the Volvo lube. Your 280 has a pump on the forward gear unless someone removed it or it has already sheared because of heavy oil. Use engine oil.