I have two 5 gallon fuel cans. One metal and one plastic. The metal one was all I could find at the time, expensive, and a pain to use. The plastic one is much easier to handle. The JD4100 is stingey on fuel. I've probably bought 8-9 can fulls of fuel since I bought it a year ago (108 hrs).
Like everyone has mentioned, go with the 5 gallon yellow plastic containers. In summer, one is sufficient. I have the two as a just-in-case for the winter.
Terry