I stopped using any oil produced from Pennsylvania crude about 30 years ago. I worked as a mechanic at the time and every engine I opened up I knew immediately if Pa. based oil was in it. The engine would have a large build up of waxy sludge in it. Most all refineries have closed in Pa. since and I do not know if there is any Pa. based oil on the market at this point. Many folks back then ran Quaker State or Pennzoil only around here since it was produced in the area. The wax build up only became a factor as the engine aged but I had cases then where the sludge would clog the drain back ports in the heads and the oil would build up and get into the cylinders via the valves. I think a lot of engines got changed or rebuilt back then that could have lived on if it would have had the sludge cleaned out and the drain ports cleaned on the top end.
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