If I remember right, you are in UK. Up here you can get all the #2 you want. If you call them early you get todays price. If you call later, they tell you “we don’t know what it will cost until tomorrow”. There was finally a newspaper story about the burden on people. Supposedly we have 40% of homes using #2 oil for heat. But nobody’s topping off that I know.
If anything they order a smaller amounts because of the high expense. but 50 and 100 gallon orders have a higher price per gallon. I get 300 gallons for the cheaper price. I use about 1200 gallons a year. No matter what the cost. And I assume the producers produce the same amounts every year to match usage. So if by you, people are topping off to avoid higher prices, yes that would be artificial demand and higher prices. Then 4 days later prices are lower and they all topped off on the highs. LOL, the system is a joke.
I remember decades ago when prices were high for gasoline. You could buy nice 4X4 SUVs real cheap, motor homes too a big bargain. Then when prices crashed, those vehicles got expensive again. In constant value dollars, in my view, gasoline is slightly cheaper or exactly right in line with 1970 prices.