Good fuel stop on the way to Oshkosh

I'll be flying to Oshkosh from the Washington, DC area this year. Two
years ago, I made a fuel stop at an airport that had a special deal
during the AirVenture event. I think the airport was just south of
Chicago. Does anyone know of a cheap place to refuel on the way to
Oshkosh?

Last year I had good deals at KFNT, they also gave us loads of
souvenirs - just because we mentioned we're on the way to OSH. If you
have to spend the night there, don't accept the FBO rec., rather take
the inn pretty much across the highway (slightly to the right) from
the airport. Cheaper and cleaner.