Ditto on non-synthetic gear oil.

 

Awesome. Gonna try to do it first thing tomorrow

 

Dana stamped on the diff cover Synthetic Only, do you think the people on this forum know something Dana doesn't? Even the new dana 60's specify to use synthetic.

 

Sorry, but the specs are for mineral oil 80W90 or synthetic 75W140 (see http://www2.dana.com/pdf/CRATE44-SPEC-5-12.pdf, second page, "Lube Options"). So, if he's not towing it's conventional or non-synthetic)

 

http://www.machinerylubrication.com/...ventional-oils

http://www.doolittleoil.com/faq/synt...nventional-oil

A very respected company with real facts on gear oil. Conventional gear oils promote sludge buildup, has a higher drag coefficient, and needed to be changed more often. The only place you will find conventional gear oils recommended being used in new vehicles are in forums where no proof is ever shown. I can say that I run manure in my axles and never had any problem that don't mean it's the best.

 

That cut sheet isn't saying one must run mineral oil and not a synthetic oil. As far as I know, one can always use a synthetic in place of a non-synthetic if it meets the oil specs. Not buying that non-synthetic would run cooler than same viscosity synthetic either.

 

I have 3 bottles of 75W-90 and another 75W-140 left over from a prior fluid swap. Has anyone mixed before and foresee any issues? They're all Royal Purple Max Gear, so same type aside from weight. I'm thinking of mixing the 140 and 90 in the rear...

I haven't seen anything other than "suggestions" (vs. Rules) using one of these two weights, so I assume this is OK.