why is my car overheating and the oil is fix in coolant resouir? on 1998 Cadillac Catera

and oil in sparkplugs

Asked by for the 1998 Cadillac Catera
Smoke or steam from exhaust? Engine oil milky in color?
Pogo stick or skateboard?
Radio Flyer.
Red Ryder?
2 more answers
Sounds like blown headgasket. Check compression, pressure test cooling system , also a chemical test kit you can get to check for combustion gas getting through cooling system.
oil + coolant = blown head gasket...