During my last two oil changes I've noticed the oil is very slightly mudded. Should I be concerned? It seems to be a very minor discoloration, the oil is just not brown but a tiny, I repeat tiny bit of muddy/flat milky shade.
This is a 2000 2.2L Impreza with 26k miles. Has been driven mainly highway at high speeds. Oil is changed every 3500 miles. Coolant is nice and clear, haven't noticed it getting low, or anything, although I haven't been paying much attention to it, up till now. No overheating whatsoever.
Please help, I would want to catch a possible problem before it gets costly, or something. Should I have it tested or just observe it for now?
MN