A few days ago I drained, flushed & refilled my YH compressor with Royal Purple. I just topped off a 30 minute SCBA & a small paintball tank (for my backpack). The oil is black again after only 15 minutes runtime. Should I drain, flush & refill again? Oil showed purple for about 45 minutes runtime on my initial fill when I first got the YH but turned pretty quickly this time around. Any thoughts/advice?