80/90 dino or 75/140 synth

[Kilgore Trout]

So my buddy and I went out to his shop to change the diff fluid. I bought everything ahead of time according to Haynes manual and owner's manual.

Anyway, AFTER we drained the diff fluid I noticed that a tag on the cover of my 2001 GT diff said use 75/140 synth only. Of course we had 80/90 dino oil

Car was apart, no choice but to use what we had... That was 3000 miles ago and so far no problems. How high of a priority should I make it to correct this situation. Do I even need to? And yes, I did at least have the friction modifier and used it to spec...

 

[Kilgore Trout]

ttt

 

[hotrodnut]

I have been told by a Ford service tech that it is okay to use what you did. That don't mean it's okay to do I guess, but I would say as long as you had the friction modifier in, you are going to be okay.

 

[hognutz]

I would switch it back over to synthetic but that is me. It is not going to die or anything. I just prefer synthetics to dino. I would search for some info on the web. pretty much backyard experts here. I do not alwasy trust the info I read on stuff like this on a message board. Prefer to get rock solid info.

that being said I am pretty sure the synthic will give you better life in every way over the dino. so since it is not realy a big cost issue just a doing it issue I would switch it back.

 

[Kilgore Trout]

I am going to switch it back when I install my gears in July. I was really just trying to decide if I could wait that long.

Found out my buddy who is a highly skilled home mechanic now has a magnetic base dial gauge and an inch pound torque wrench so it should be possible to do it myself with his help and tools.