Sorry people, the fuel make is not what I called it, the fuel make is "Cool Power" -15% nitro four stroke fuel, thanks w8ye for the correction, that's what I meant to say. The exhaust oil is also not black but grey, I use the word black-ish in colour but the run-off is actually grey. Last night I removed the cowl and checked the header and muffler; the muffler was slack. I tightened it and used some HTV black silicone on the threads to seal it, I will run it today and check the oil again to see if it is clear or less grey. I do not believe I am running the engine hot as the mixture is very rich, nearly 1000 rpm below the max, and correct the 16x8 prop is over-sized, I will use a 16x6 instead to help with better rpm's.<div>I am leaning on the assumption that the grey oil is wearing-in of the sleeve and ring and that it will go away eventually, I certainly hope so. Standing by further.</div>