I apologize if this question has been beat to death, I did a search on the forum for my answer and found conflicting answers, so I had to start this thread. I bought the Mopar differential lubricant from the dealer and took it to my mechanic and he forgot that I had bought it and set it on his shelf and overlooked it and ordered Valvoline syn power full synthetic 75/90 and told me it was a better lubricant and to take the 2 quarts of Mopar stuff back to get my money back. The car is still up on the rack and this morning I asked him to drain it out and put in the Mopar stuff I had brought to him. I haven't gotten a reply yet. He has a shop with several Vintage restored Fords, Chevy's and Dodges and a TR-4 he is working on. Will this Valvoline lubricant work properly or turn into molasses like another post I read. If it will work, then I'll call him and tell him nevermind the fluid change. What do yall think? Thanks in advance. Peace.