I'd be amazed if your Poulan oil caused your engine to run significantly slower. It's very hard to measure a repeatable difference in rpm by switching between brands of oil. Less oil does not create more power, despite what same may believe.

Some props pull a lot better than others. You can't tell how good a prop is by what rpm your engine will turn. You just have to make sure your engine turns in the right rpm range to make it happy. Try a 20x10 Mejzlik or a 20x10 Airwild NX or a 20x10 Menz-S.