I have a 2002 XJ8 with 145K miles. I noticed a slight plume of oil coming from the left front corner of the engine. What could this be? The oil is not dripping onto the pavement nor its being sprayed on the engine.

 

Well, you could start by cleaning the part load breather and the full load breather. At least then you might avoid crankcase blowby pressure. There's a lot in the archives on the procedure. Just make sure you don't drop anything into the engine. Also, the hoses/pipes are getting brittle by now - the breather hoses, so be careful. The part load breather hose is sort of a pain to replace. I replaced mine when I had the intake manifold off, but it can be done without removing the intake.