So Nick can you use synthetic oil? Even if it has the GL4 rating.? The Sta Lube product seems to be the only thing that is not synthetic and has the GL4 rating. Apparently all the transmission lube is now GL5 or GL6 --that is the stuff that destroys the "yellow metal" --brass and copper used in these Muncie , T10 and Super T10 transmissions. The StaLube GL4 non synthetic is not allowed into Canada. ( I thought you guys where building the wall on the southern border) Or maybe we are building the wall. This is pissing me off . We do not need walls, I just want to buy some tranny lube. that will not destroy my transmission. Morley