Surprisingly, there don't seem to be any threads on this yet. If I want to add oil to my AC system (2004 XJ8, no rear AC), but I don't want to remove the compressor, do I add oil thru the low-pressure port, high-pressure port, or compressor oil service port?

If I add it to the low-pressure port, is it by gravity feed?

Does the XJ8 AC compressor have an oil service port?

I can't even find the compressor, despite having its location pointed out on an X350 manual page (along the centerline of the engine compartment, just behind the radiator cap; height is not specified but it must be below the engine).
If it has an oil service port, it seems I'd need to get underneath the car to find it.