Well guys, the Detroit Locker will be coming out this weekend and the 3rd member rebuilt in this thread will be going in. Based upon the recommendation of Eaton I will be using a Mineral gear oil without any FM added. I elected to use Walmart SuperTech 80w90 for now. Will likely run it for a week for my normal travels (~150 miles) and dump the initial fill. I will then run the refill to the next oil change ~4500 miles and change again. What's a good OCI to use for mineral gear oil? It's been years since I've run one. I was thinking 15,000 or there about. As an added note I did submit a sample of the Redline Heavy Weight Shockproof that's been in service just shy of 49,000 miles to Blackstone for analysis. I expect iron to be high as a result of the ratcheting action from the Detroit but time will tell.