But when we’re talking about getting the most fun from the least amount of fuel, we really have to talk about motorcycles.
It’s the logical conclusion of the low-weight, small-engine formula: just about any old bike you can buy will weigh half as much as a Caterham. From there it’s really a matter of where you want to go, how much power you want to put there, how much weight you’re willing to carry and what you want to achieve when you gain weight.
Take the Ducati Panigale V4 SP2 as an example. It is broadly a road bike with number plates; a spine-destroying, ego-devouring bike with a supercar-smashing power-to-weight ratio and more motorsport gubbins than a season of Ride to survive† It’s pretty pricey for a bike (£35,000 isn’t exactly peanuts), but it’s the least fraction of the price of a supercar and it will do 35mpg without a worry. And that’s about as bad as the average customer can do in terms of purchase price and fuel economy without a) buying something custom, or b) buying a Harley.
Something like the Suzuki SV650, on the other hand, weighs 200kg, has 72 horsepower, delivers 68 mpg and costs £7,000 new. If that’s not frugal in your book, you may have a future with the landed gentry.
But being the sycophants of lightweights that we are, we pay more for less. Cue the Husqvarna 701 Enduro. For around £9,500 you get a bike that weighs 150kg, has 74hp, has 67mpg and has the off-road capabilities of a steroid goat. So whatever you like will take you where you need to find it.