My Trianco Contractor is 11 years old. For a while now it has smelled 'oily' when on, and at the last service I mentioned the slight oil show which was to the side and just below the combustion chamber. He didn't seem to think much of it. I asked if it was due to 'over fueling' , ie un-ignited oil being sprayed before ignition or after shutdown. He dismissed this idea. However, the smell gets more noticeable and I assume it's from this unburnt oil being warmed up by the heat of the chamber. Looking under, there is a bigger patch. Any thoughts ? is it a leaky valve in the nozzle feed ? It's a Riello burner. Thanks for any insights.