If the oil was grey in color with a metallic look to it, that usually indicates a worn clutch. Especially if the metallic particles are non magnetic.
If the particles are magnetic, that could be worn gears or something that has broken inside of the engine and is being ground up. Don't run the engine until you find the problem or it could self destruct.
If the oil is milky in color, that usually indicates a bad water pump seal.
Make sure you are using 50/50 coolant and distilled water in your radiators. If you are using regular water, this can cause oxidation problems in your coolant system. This can show up as small flakes in the coolant.