What gear oil should i use for m20 and how much do i fill it?

 

Regular SAE 80W90 gear oil is fine. 70W140 synthetic is overkill, but also fine.

You can look up the quantity on the interwebs.

- Eric

 

I just put new fork seals in mine and the man that sold them to me said that he did not recommend using synthetic oil in the Muncie because they tend to leak with it.

Has anyone experienced this?

And what about the 75-90 synthetic? For some reason it is much cheaper than the 70W140

 

I'd use the 80/90 wt non synthetic. Fill to 1/2 inch below the fill plug hole located about 1/2 way up the side of the case. I usually push my finger through the hole and fill until I can touch the oil by bending the first digit of my finger.

 

X2, I do the same thing with the rear end gears.

 

Also make sure it is GL4, not GL5.

 

X2
Muncie's don't like synthetic gear oil.

 

I had a bunch of Red Line synthetic gear oil at work so I figured what the heck and filled up my Muncie. Came out to some puddles under the car and got to checking it out and the oil was bleeding right thru the porous casting. No matter the wt of synthetic it always seems light. Put good old 75-90 back in it never had another leak.