but you have to kill oil men 4 times. I filled up before this stage on blue runes so I had 8 bars of them. I didn't use the void power until the last time, ran around and used it again until all of the oil men were gone. Then I could focus on the wheel alone. There may have been 2 oil men left though.
The only hard part is running around in circles leading the first 3 sets of oil men away from the wheel.