I've been monitoring my oil usage after some work was done, by using a tape measure on my tank's site gauge.
According to my EPC, my house's heat demand for space heating is around 30,000 kWh per year. Typically, I have the hot water on for 2 hours a day and the heating on for 6 hours a day. I believe my boiler is around 20 years old. My measurements were working this out at around 10 litres per day, which didn't seem unreasonable.
Yesterday, though, I just had the heating on for 1.25 hours and the hot water on for about 2, and I measured this as 5 litres!
Tonight I sat with a book in front of my boiler. Initially it fired up continuously for 45 minutes. After that, though, it seemed to fire up for roughly 2 minutes 20 second, then shut down for 1 minute 10 seconds and kept repeating this (originally I was writing down start and end times, then I used a stopwatch). Can that ever be normal behaviour for a boiler?
Edit: sorry, no, I can't smell anything at all, although the oil pipe is underneath concrete so I'm not sure I would?