why am i burning oil?

[Bigcheck1]

yesterday, my oil light came on when i started my car. it was right around 30 degrees out. i checked the level and i was a quart low, first time it has ever been low. i put a quart in and all seemed fine. my roomate was following me and he said that i had grey smoke coming out of the exaust and it smelle like burning oil. what causes this?, i need to get it fixed and i want to have some kind of idea as to why it is happening. any help would be great...
thanks

 

[Tars]

Might be valve guides/seals. My 4.0L doesn't use any oil, but my friends girlfriends moms(I hate those chains) Explorer used a ton of oil. She ended up having the heads pulled and new guides and seals put in. Last I hear it is still working ok. The work was done four years ago. To answer your question as to why it is happening, when those parts get worn oil leaks past them and down the valve where it enters the cylinder and gets burned with the fuel.
It could also be a bad oil ring on one or more of your pistons. Thats what I would think it is. Let me know what you find.