All Pennsylvania oils are high in Paraffin and will leave deposits.
My brother in law worked as a Ford salesman for a long time. The older folks that would buy Mercury Grand Marquis, Crown Vickies and the like would tend to get their oil changed at the dealership. For some reason, at that time, the Blue Oval camp was using Quaker State in the cars. Well, after these cars had 50K or 60K on them, all slow driving by these seasoned citizens, they would develop blue smoke on startup. After pulling the valve covers, there would always be this gloppy waxy goo all over the valve guides--paraffin. It would creep down the valve stems into the combustion chambers after shutting the car off in the evening. Then, in the morning, after starting the car, it would burn and smoke would come out of the tailpipe.