They were the future, once. Back we decided that using no fuel at all was the way to go, these cars were designed to use as little of it as possible.

First up, then, the Toyota Prius, the original petrol-electric hybrid vehicle for the masses. It looks conventional (ish) but housed what was, at the time, a truly unusual powerplant.

It was followed by the first-generation Honda Insight, the radical-looking two-door coupe that put aerodynamics and compactness at the centre of its ability to return 100mpg in careful driving.

And then, finally, the most exotic fuel-saver ever created. Volkswagen's XL1 was original conceived as a 'one-litre' car, one that would sip fuel at just 1 litre per 100km (or 282.5mpg). It's impossibly light, inconceivably small, and beautifully constructed from carbon-fibre and unobtanium. VW only made 250 of them and they need very careful looking after.

Join us as we test these three landmark cars, and ask: what did they teach us, and how do they stack up today?

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