Magnatec 10/40 oil

[Bob Culver]

The VW Beetle with bearings less absorbent than white metal, ran with no filter and 3,000 mile changes at least until the early 70s. In 1970 API SE was the standard; not as detergent as later but early cars would have been run with lower detergency oils and changed to SE. In all  cars current more detergent oils would have been used in following decades. I dunno whether the very late South American production had filters. 
With Sevens a magnet seems desirable to collect the timing gears.