My son has a 2002 rubicon with 700 miles. It has always been service and has never used oil. Saturday he was riding it and noticed that it would only run 47 mph. It used to run 53. Pulled the air filter and found it to be full of oil. The engine is putting oil into the air filter box. It appears to be coming from what looks like a breathe tube going from the air box to the motor. Has anyone had this to happen and if so what has happend to the engine. It still runs smooth. All help is appreciated.