i pulled my spark plug wires for the first time ever since buying my car....and i found oil in there....especially the 3rd one it was like filled...does this affect anything?? my gas mileage is like 200 miles per tank can this be the problem?
sorry if it's a newbie question

 

which car, what motor.......
i get about 280-300 per tank, depending on how i drive.
yes, oil should not be in the hole with the plug and boot. its most likely due to the seal around the hole for the plug wire in the inner part of the valve cover. very easy to change, each gasket is like $4 at the dealer.
search and you will find instructions on how to change the gasket.

 

it is a 91 ls b18a motor with 205k miles still run strong but burns alot of gas.

 

Like he says, its most likely a valve cover grommet. Theyre only a couple bucks, nothing to get worried about yet.