http://www.automobileglobe.com/know-about-oil-leaks-into-spark-plug-well/ but this article will x-ray the main causes of this situation

Leaking Valve Cover Gaskets:The valve cover is a metal unit found on the top of the engine, this seals the engine and helps prevent oil leaks. Between the valve cover and the engine are gaskets that has the tendency to fail over time. Due to the high temperature of the engine the gaskets can get brittle, and start to leak. It is possible for the oil to leak into the spark plug wells. Leaking valve cover gaskets need to be repaired or replaced as quickly as possible, failing to do so can result in further damage to the engine.
Failing O-Ring Seals:There are O-Ring seals found at the bottom of the spark plug wells and if a seal begins to fail, oil can leak past these seals and into the spark plug well. Again, this issue should be replaced as soon as possible and the spark plugs should be changed as well.
Failing Piston Compression Rings:The pistons in a vehicle’s engine have compression rings at the top of the piston and the bottom. These rings are arranged in grooves in the piston and help scrape excess oil from the cylinder walls and stop oil from getting into the combustion chamber. If these rings fail, oil can make its way into the spark plugs wells. Other signs of failing compression rings include increased exhaust that is blue and smells oily.
Failing Piston:A piston that is going too hot can develop a hole or crack. The most common signs of a failing piston include rattle and knocking noises while the vehicle is running, excessive oil burning as well as a loss of power and engine misfiring. It can also lead to oil in the spark plug wells. This is an extremely serious situation that needs to be repaired as soon as possible.
Bad Valve Guides:Valve guides help to moderate air intake by keeping the valves in place while the engine is working. Over time, valve guides can become extremely worn and will need replacement. Blue smoke and oil or ash in the spark plug wells is a common symptom of failing valve guides. Worn valve guides can result in more serious engine problems and should be repaired as soon as possible.
http://www.automobileglobe.com/what-are-the-causes-of-oil-in-the-spark-plug-well/

Thank you.. But I don't have a car yet and when I do the mechanic will work the math out. ...

lol..cooool