Interesting how motors without filters did well.I now have even more respect for my 1971 Kohler ball bearing powered Wheel Horse tractor... it had no oil filter and still runs great today with no engine repairs..
My 73 VW of course had no filter. Changed oil every 2K. When it neared 100K it dropped a valve. When the engine was disassembled it looked like it had just left the factory. No exxageration.