I have a 67 Mustang and need to replace the oil in the rear axle. What weight oil should I use? I have ordered a shop manual so hopefully I will be able to answer these questions by myself from here on out. Thanks for the help in advance.

 

i usually use 75W90. works well for me. and royal purple at that. personal preference.

 

I run 80W90 in mine. I don't ever see 75W90 here. Don't forget the friction modifier if its traction lock limited slip.

 

I use 90W in mine

 

Did you notice any mileage gains when you started using Royal Purple? Did you switch from a non-synthetic?

 

i did, but the problem is what to give it credit to haha. i tend to do things all at once, not very scientific regarding variables i know. i did the diff lube, tranny oil and filter change, engine oil and filter, general tune up (wires plugs rotor condensor distributor cap), and even a carb change (old one crapped out).

 

I run Valvoline durablend for oil and gear lube.

 

I use Mobil 1 synthetic in all my street vehicles and race cars. Break them in with mineral based lube, then switch to the Mobil 1. No problems in 24+ years of racing. Buddies use Amsoil, or Royal Purple. Personal preference, they never have trouble either.