over the past few years i've collected a few quarts of Redline from trans fills that didn't require a whole quart. is this stuff ok to use still? been in the garage with 4 seasons....
If capped tight, I wouldnt worry much about it... though I might blend it in with some new fluid.
Usually I try to mix older stock into new opened bottles when I do something like a diff or trans that leaves some... this way it gets used up and I keep newer stock rotating as the open bottle.