Was supposed to post this ages ago, just forgot.   At my last service my mechanic said he found oil in the back 2 spark plug wells, he said it was not sever, like it had built up over time. I heard that 04's are known to have poor cam covers which can cause this?   Iv'e also heard many other terms and i think i need some education, can someone please help me understand all the different things listed below (iv'e heard them at some point in time) and what they do, difference between them, if