Believe if storage is for more than year. Empty or run tank dry. Add about a gallon of thin oil to tank. Crank over until system is full. I would change this oil probably every three to five years. Especially on mercedes with two zenith carbs. Probably should buy specific storage oil somewhere but almost any oil is better than leaving gasoline in system long term probably. Some additive or process in our regular gasoline seems to make it go bad faster than in old days. Our premium grades are a little better in storage situations.(canada) Above info obtained years ago somewhere but have never forgot it. Now only if i could disipline myself to put it into practice myself. Oil swells and eats rubber so maybe better off using transmission fluid. It's the old story of not enough time to take 1/2 hour and do it now but book a day or two in future to clean up mess and vent your wallet. Any opinions?