I've been needing to ask for what oil anyone might recommend for an 82' 633csi? (or any similar e30 engine) I live in the pacific northwest so the climate is moderate at around 40-50˚f year-around for the most part. The owner's manual suggests either a 20w-50 or 15w-50. I haven't had the car long and I'm not sure what oil was previously used. Any ideas?!