Aimed primarily at bi-weekly customers, particularly during a stretch of weather where those 14 days in between checks can feel like months, it is important to know the science, or lack thereof, when it comes to automatic delivery be it oil or propane. While lending a degree of comfort knowing that your heating fuel provider has you on the schedule, the delivery dates are based exclusively on historical usage which of course is based on patterns of usage. The curve is bent when family is in town for a week and the heat setting goes from 52 to 68 or when a painting crew bumps it up to 70 for the +/- 10 days they are in house sprucing up the interior. While rare, it only take a week of unseasonably cold weather to take that third of a tank guesstimate down to an eight. I usually make the call at a quarter tank but for those disrupting the trend for any number of reasons, keep your fuel provider in the loop.