foam air filter without oil?

It's a generator, 5000watt, honda. It's in a small shed and nj suburb, everything is either grass or asphalt. The shed sees little dust, landscaper. Original filter was factory oiled but designated replacement is wrong size. So bought UNI foam filter (green and for fine particles, 5/8" thick and plan to double it) and a can of spray oil made for filters but wondering if oil is a must in this situation?