Phillip's Milwaukee Distributor usually has cases of aviation oil (Semi loads) discounted for sale out of a tent at Air Venture. They usually have golf carts and will deliver anywhere on EAA grounds even to your car in EAA parking lots when purchasing 2+ cases. The only snag is the deliveries are made first come first served and they are busy which can eat up some time waiting. You ride with them in the golf cart during delivery. I have bought from them for years any where from 2 cases to 12 cases at a time & they do price it right. I can't tell you where they will be located but I would be surprised if they are there...I have done this since the mid 1990's.
ATW is just a few miles north of OSH so this should be doable.
Dick DeCramer
Faribault, MN
RV6, RV8, RV4