In six years of ownership my old Toyota Avensis never used a measurable drop of oil between services. The Leaf has no oil to check or change.

Indeed, I can't remember the last car I had that needed oil in-between annual changes.

It is impossible for an ICE not to burn oil, even with modern engineering's tight and precise tolerances. Many amateur mechanics are ignorant of fuel dilution (google it). Some engines, especially diesels, are more prone to it than others. If the oil is diluted with fuel at the same rate as it's burned, the amount of liquid in the sump will remain the same. In the old days, this was a good reason for changing the inevitably adulterated oil more frequently (my 1980 TR7 handbook recommends every 6,000 miles - which I have always studiously adhered to).

Good point well made.

Fuel dilution has ALWAYS occurred but wasn't noticed on petrol engines as the petrol evaporates each time the engine warms uo - unlike a diesel which struggles to warm-up completely in winter and the fuel has a much higher evaporation temperature.

Failed DPF regenerations increases the rate of fuel dilution, particularly affecting modern diesels used for short runs.

I guess most of this fuel dilution happens while the engine warms up, which (at least for petrol engines) is why long journeys are better for the car than many short ones ? Once everything is warm, petrol will vapourise from the hot oil. If the oil level in a car used in that way remains the same, I think it is reasonable to assume that very little oil is being lost - which can happen in other ways than being 'burnt'. I'm sure many of us have had cars which needed new stem seals, for example ?