Gas stains

[edschwab1]

I finished working on a boat yesterday, but was unable to remove what I believe is a gas stain. The stain looks like heavy oxidation, is under the gas cap. I tried PI-III ECRC x3 and PI-III RC x3 on the effect area. This process worked on the the rest of the panel to the portside of the gas cap, which was looked the same way. Is it possible to remove the stain?

 

[Thomasfl]

good question, I detail an Escalade every month that has slight gas stains on the plastic panel under the tank. I have tried everyting, posted on it a few times with no luck.