Lots of factors to apply but it mostly depends on the size of your home, the efficiency of your boiler and whether or not you’re also heating your hot water with oil. For days that are bitterly cold, which would be 10F and under you can anticipate burning between 5 and 10 gallons A DAY. This time of year it is closer to 1/2 to 3 gallons. When I first bought my home I kept a spreadsheet of every oil purchase, how many gallons it was and the price per gallon. Really, the old saying is that during heating season “Order at a quarter” to allow for up to a week before delivery can be made. Ultimately it’s your choice who you buy from and unless you go with a large oil company who does payment plans, you pay the price the market sets or whatever discount you can find through smaller cash only oil companies.

If you want more info please feel free to ask, no better thread to ask questions in.