Oil Boiler into energy dashboard through a physical gauge

In my quest to track my heating consumption through my oil boiler, I want to integrate its consumption into the Energy Dashboard.

I have an oil boiler of which I know the capacity, and I have a gauge that tells me the remaining amount of oil. I want to create a sensor that I could integrate into the Dashboard that would calculate the consumption based on the capacity and the remaining amount.
I envision an input where I would indicate the remaining amount each week, and it would calculate the weekly consumption and could also compute the daily consumption, weighted by the average temperature of each day.

Has anyone done something like this before, or does anyone have any ideas on how to achieve it?