Hello everyone. I'm good a reasurching the internet I have an issue I just can't figure out. So I'm turning to you brains to help me. I have a 2015 F-350 diesel that is a cab and chassis. I just ordered and received a brand new Dana 80 rear axle. I also ordered two bottles of Yukon Friction Modifier. The Dana 80 box states for me to run 80W-90 non synthetic. Apperently synthetic oil makes it to aggressive on the limited slips,, whatever that means.. I'm an Amsoil guy but amsoil is synthetic. So I go and buy some Valvoline 80-90 and it says for limited slip use as a top off only. I can't win. I finally did find a STP brand I can use but UGH. WHAT DO YALL DO? second thing is if I'm pulling alot is 80W-90 even thick enough or should I just follow their instructions?

Thanks guys and girls

 

Call your Ford Dealer and see if they have C8az 19B546 a additive
Ford has used that for years