Since I do it myself, there is little cost in oil changes. In the warm climate of SoCal, I don't need the cold weather flow advantage. I use Castrol 5W-30 and plan to change oil and filter every 5000. I read on another board about someone putting a supermagnet on the bottom of their oil filter to hold (iron) metal filings on the filter. This is a bad idea! If that magnet gets knocked loose, you send a gob of shrapnel into your oil galleys! My (air-cooled) Volkswagens use a magnetic drain plug, but that was permanently attached and actually did some good. (Interval is 3000 on those cars since they have a screen and no filter).
