Last summer I went from shelter island to Huntington through the sound. I would say the first 2/3 of the trip was smooth and the last 1/3 was choppy but still doing 22kts. My 02 340 with 8.1's went through 3/4 of a tank of gas. It was eye opening how little economy I was getting. That's one of the main reasons I moved to diesel. Coming from the west, there is gas in manhasset bay, glen cove, oyster bay, and Huntington. I know there is also gas in Stamford which is slightly cheaper than the ny side.