A garage in town told me they were sticklers for using "correct parts including oils. So I asked them to change the rear gear lube and they puyt in 75/85 weight when the OM says to use 85/90 weight. When I asked a more independent garage owner (much smaller) he just sighed, shrugged his shoulder and said : I guess it will be ok, but the book recommends 85/90.
So am I shooting myself in the foot leaving this lighter lube in the differentail case?

 

Seeing you're in Texas where it gets hot, I'd put 85/90 in it, If you lived a lot farther north I'd say you would be ok.

It would also depend how far you drive, if you're only driving 20 or so miles at a time you should be ok.

 

Vehicle is a 2.3 Duratec, but I'm not sure if its a 4 or 5 speed automatic. (oh boy - probably 5)) It has 120k on the clock. It was a Fleet vehicle up to about 100k
It seems to run ok, no leaks, 20 mpg, cold AC set at about 3 out of 5 on cold scale, inna heat.

Your point may be a very good point! Yes to warm up everything up once a month I like to run it out I10 and back for about 20 miles at 60-65mph, but sometimes that goes out the window and I find its much safer at 70-80mph. I drive it 50 miles on occassion as well, at about 60, but yessir, 20 miles sounds about right on average. jeeze, I AM old.

What would you say about changing the AT fluid. Its lite brown. The owners manual says to change it and the filter at 150K. What might I want to use to refill it with? Ford fluid?
Thank You Very Much.
Stanley