Just a note to pass on to Canadian Ironhead riders. I have had an increasingly hard time finding straight 50 oil for my high mileage 82 Ironhead close to where I live. Discovered our local Canadian Tire store carry's Motomaster Heavy Duty 50 wt. diesel oil, at 20 bucks a 5 liter jug. Did some research and found that it is repackaged Shell Rotella T. (All oils sold under the Motomaster brand are made by Shell) Not the cheapest around, but readily available. On my 3rd oil change now and no issues so far. Engine seems to run quiet and cool, and uses no more oil than before.