@Mustangman–When we used Quaker State in the 1954 Buick this was back in the late 1950s through the mid 1960s. We used straight weight oil–30 weight in the summer, 20W-20 in the fall and spring and 10 weight in the winter. I wonder if some of the sludge you experienced may have been due to the use of 10W-40 oil which was popular back in the 1990s. The owner’s manual for my 1978 Oldsmobile recommended either 10W-30 or 10W-40. I used the 10W-40 and had problems with pre-ignition due to carbon build up. I would have to add a can of Casite motor tune-up to the gasoline about once a month and would also pour Casite through the carburetor while the engine was running to alleviate the problem. I then heard, ironically on Cartalk, that certain 10W-40 oils in certain GM engines would have this problem. I switched to 10W-30 and the problem of pinging on acceleration disappeared. I used whatever brand of oil was on sale in those days. Apparently the polymers that were put in the oil to extend the viscosity range to 10W-40 was the cause of the carbon build-up.