Synthetic or Regular

[Rat]

Had 4.10's installed and the shop used regular Ford 85 90 or something similar with the 4 ounces of Friction reducer said they did not recommend Synthetic because they had a few instances of clutch failure with it. Should I have the oil changed to synthetic or what is the going opinion on this. I ran a search but didn't have much luck. Does Synthetic still need the Friction Reducer? Got about 500 miles and everything seems ok.

Thanks:
Bob

[Mikeenh]

Rat, I had 4:10's installed by Dennis Reinhart back in January. I used synthetic gear oil then. I probably have put 15,000 miles on since then....no problem. I'm sure this is just like what type and weight of oil you use in your engine.......a million opinions.

[jgc61sr2002]

Rat - If Dennis uses synthetic oil, then that is the way to go.:D

[joflewbyu2]

highly recommend amsoil 75w-90 synthetic. superior to the mobil 1 syn gear lube. still use the modifier- just for extra precaution. the factory does indeed use synthetic as factory fill. they don't recommend a change for the life of the diff unless under severe use where they recommend 75w-140 synthetic every 30k miles. i put on the svo rear girdle and stud kit. the billet heat treated thick cover has a drain hole for easy gear oil change. did the cover at 7,500 miles and then changed the oil again at 10,000 miles.