Good advice, Alvin,
My 10+ year old Harbor Freight 80 gal 5HP 2-stage compressors lives/runs in a garage bay separated from our work bay (I am lucky to have a large garage). The oil has never been changed (it looks to be clean) - nonetheless, I should have changed it.
Another maintenance recommendation: drain the tank as often as necessary. Here in NY, at least once a year (before winter hibernation) is all that is needed - but it is needed (and, that water would freeze during hibernation).
