I was replacing the air filter during the 12k mi. service. Once I had the old filter out, I noticed a little oil was being spit out of the rear right hand intake, and lightly spattering the intake throat and a couple of inches around it.
Every engine builds up pressure, there is a vent somewhere on the engine. Most "driveable" engines have them go to the air filter box so that the gases released are circulated back into the intake to be burned off.