I'm still waiting for someone to step forward & properly challenge me & my little Suzuki Celerio.
I once, on a long motorway run, got 546 miles on 32 litres (8.45 US gallons) of standard UK unleaded. Compared to any hybrid, the Celerio is laughably low-tech (& dirt cheap to buy) but it does demonstrate just what you can do with low weight, a 1.0 L 3 pot NA engine, a relatively high compression ratio, good gearing, 0W20 & a light left foot.