My Dad had a oil filter that was a cannister with toilet
paper for the filter, in his old Ford Truck. It was an
accessory filter and the oil looked very clean between
changes. Ah, The days of non-detergent oil. I believe
it was called the Franz Oil Filter.

http://home.earthlink.net/~goodspeeds/LSANDRA.HTM

Some info on the link above. Should be more on the
internet. I believe Hengst has an accessory filter too.

Gary