Red stuff is what happens when you use ethanol blended fuel, like E10 etc. Fucks everything, if you wanna use e10 you must use it in 95 octane blend (read label at pump cause you can get e10 from 89 through to 101 octane at different servos)
Had this issue heaps when e10 first came out, people didn't understand that the car said it was ok but didn't read the fine print as to what blend to use, Replaced many of plugs for engines running rough from it haha
Many people pretty shitty cause they all thought it would be under warranty.