Ok, I know this is a dumb question and I'm not a mechanic nor am I foreign to the automotive scene, but one of the stupid things I never figured out was about oil types. Simply put, could someone please tell me what the difference between regular old oil and partial-synthetic and full synthetic is? I never really thought about it till lately. I noticed the full synthetic stuff is a lot more expensive so I figured that this must be the best kind of stuff, but I wasn't sure. I have an '86 300E and I don't like to skimp on maintainence stuff, I try to buy the best (and most expensive) stuff for it. Can someone key me in here, should I be buying stuff like full synthetic Amsoil and Redline or should does it matter if I buy regular Penzoil or whatever?