You can delete one if you want.

The 30% nitro is awesome in a 4-stroke and even YS recommends using 20-30%. It's only a cost issue that people don't like. It makes a big increase in performance. The only thing I can say with 4-strokes is to add castor or synthetic oil to the fuel you buy at the store to bring it up to 20% lube. The engines last a lot longer. 4-strokes need plenty of oil.