Anyone know the real story for SLP's Blackwing (was Donaldson) Air Filter Cleaners -- can K&N cleaner & oil be used, or do you have to use the Blackwing stuff? SLP claims you need to use the Blackwing cleaner & oil... K&N is cotton with red oil, Blackwing is synthetic with blue oil (it seems)...

Is there any other cleaner/oil that can be used? Fram has a SynWash Air Filter (synthetic) that seems to not use oil at all...

TIA!