Bob and Jean Webb

    the oils listed in the manuals has been obsolete for decades. they carried an SC API spec. those oils have no comparison to any oils blended today other than the viscosity. 20W50 is a multigrade oil that can have the properties of either an SAE 20 or an SAE 50 under certain temps. it can be used. you can use an API GL1 lube since these transmissions don’t operate under what could be called severe duty. there is no need for friction modifiers or extreme pressure additives in the alpine trans. detergents in engine oils chemically neutralize acidic contaminants but since there is no combustion in the trans there is really no reason to use a detergent oil other than it’s easy to find .with that said, I use an SAE 30 engine oil in both my non OD trans and my OD trans.