Comparing conventional non-hybrid diesel and petrol engines with equivalent performance, which generally uses fewer litres of fuel to produce the same work?

Correct answer

The diesel engine, as a general tendency in that comparison.

Diesel generally uses fewer litres for equivalent work because of its efficiency and diesel fuel’s higher energy per litre. This is not guaranteed for every pair of vehicles: compare model-specific certified figures under the same test cycle and consider actual use. Lower consumption in litres does not automatically mean a lower total purchase, maintenance and fuel cost.