Same here. Tank gets filled every spring when the price drops. Last furnace lasted 37 years till the fire box cracked. This furnace is only one year old and still on warranty.Nope. Furnace gets a cleaning every year under contract. Fuel that is pumped out of the tank during the cleaning is fine, no contaminants. Filter is changed, old filter shows no signs of contamination. Never had an issue in the 30 years I've been here.