Take the oil cap off and look to see if it has milky residue on the backside, that will tell you the headgasket is blown as oil and af are mixing. If that does not show anything, get some PH paper and rub it on the residue. The PH balance in the oil or af will turn the PH paper a certain color. If the color is a combination of oil and af then there you go. A PH chart will give basic properties/colors etc.