Actress Hailee Steinfeld pairs a navy-and-white dress with white strapped sandals at an event in Los Angeles in 2013.
If the oil is on the inside parts of the spark plug like the bottom insulator, that's a bigger issue, you have either leaking valve seals or very leaky piston rings. If your car blows a puff of blue smoke on startup, you probably ave leaky valve seals. If it blows blue smoke all the time, leaky piston rings.
One possible cause of dieseling is the use of cheaper grade fuel and oil. Whenever an engine burns lower quality fuel, carbon deposits often develop on the valves and pistons moving rapidly within the combustion chambers. If a carbon deposit causes the piston to rub against metal, a hot spot could easily develop.