Recent thread over on BNO on this topic.
From there, seems between us all, MCI has either 7 US gallons or 8 US gallons for an oil change with filter, depending which manual you refer to.
try filling with 7 gallons, run it and let it drain back down for a few hours, and then using the above technique for finding the right level, dip the oil and guestimate where it might be at that time.
Since busnuts are prone to changing their oil earlier than recommended change intervals, and keeping closer watch than a commercial coach driver might on fluid levels, even if you are running 7 when you should be running 8, I doubt it will matter. Especially when it wants to puke the first gallon in your current situation....
whatever?
happy coaching!
buswarrior