Jim,

Check your oil reservoir. That is the only other oil in that vicinity. A little toward the centerline of the bus is the oil supply and return lines from the alternator, but I would think if it was coming from the alternator or the lines you would not confuse it with the AC compressor.

Did you add oil? If you had oil on the floor, if it came from the compressor it would look clean like oil you added to the reservoir.