8kw Onan diesel quiet generator

White smoke in the exhaust is often associated with water. Keep an eye on your coolant level just in case and your fuel quality. It sounds like you let the coach sit since last fall when you added the fuel stabililzer and biocide. You may have condensation in the fuel. That would not be good at all. Did you store it with the fuel tank full? The less air there is in the tank the less condensation you will get. Also, it is recommended that you run the generator monthly for 2 hours at a time under load. Have you been doing that and running the main engine as well? Is there water in you main engine's water separator?