Typically heating oil can provide a little over 10 kWh/litre but that doesn't really tell you anything useful. What you are interested in is what heat you can put into rooms and that depends on the efficiency of the boiler, the size and efficiency of the radiators and the losses in the pipes all of which are highly variable. In addition the amount you consume depends on what temperature differential you are trying to maintain between the inside and the outside, the surface area of all walls, ceilings, doors and windows, their thickness and their k value. Again all highly variable parameters and it is not a complete list. You can't even draw conclusions from practical experience. I have burnt as much as 2,000 l in a winter but I know people who consume about 500 l for a similar size and specification house.