Gl5 was an option when I was in High School... That might have been a while ago.

Gl5 dates back to at least the early 70's.

In my experience, Mobil 1 that says "for LSD units" will chatter. My testing showed that Redline GL5 with LSD additive did not. What you need: Any high quality GL5 and enough anti chatter additive. The factory additive from Mits is expensive.

Years ago I built a custom LSD and had a chatter problem, the only lube that worked was Redline. I actually found that it was too slippery and bought the non LSD GL5 gear lube and added the Redline LSD additive separately; putting in just enough to get it to feel smooth.

If you still have the owner's guide in the glove box go out and check it, it calls out GL5 for the front rear diff for non LSD units. Same thing with the service manual: 80W-90 ( I use 75W-90 synthetic).

For LSD units the service manual calls out Mitsubishi PN 8149630 or equivalent. That is a Gl5 with LSD additive.


GL5 Redline


Redline Gear Lube Without LSD Additive

Redline LSD Additive

For most applications, a good GL5 dino base gear lube will work, its just a matter of getting enough LSD additive in it.

For a more demanding application, I went with Redline, I'm sure there are other synthetics that will work, I stopped testing when I found one that worked.

Short Story? Check the owner's manual, it says Gl5, make sure you add enough LSD additive. I have been using 75W -90

BTW, I typically pay about $15 or so a quart, 2X the cost of dino, but less expensive that some of the factory fill synthetic gear lubes.

Decent Read

Overview ASTM Standard from 1972 lists GL5