The Alfa Mito 1.4 Multiair, BMW 320D Efficient Dynamics, Honda CR-Z, Mercedes E200 CDI Blue Efficiency SE and Volkswagen Golf GTD may seem an odd group of cars.
But they all have some key features in common: 0-60mph in under 10 seconds and average fuel consumption above 50mpg.
What makes this fascinating is that the cars' makers have gone about achieving these results in different ways.
The Honda CR-Z is the first sporting hybrid. It's propelled by a 1.5-litre petrol engine that functions in tandem with an electric motor, the two combining to produce 122bhp. Co2 emissions are 117g/km.
BMW's 320d Efficient Dynamics is less technically adventurous, bigger and heavier. Yet the 161bhp diesel scores 109g/km, out-accelerates the Honda and can carry five.
The Mercedes E-class Blue Efficiency produces its 134bhp at a low 2800rpm, and manages 137g/km.
The Golf GTD is perhaps the least radical car here, although its 168bhp 2.0-litre common-rail diesel is one of the best in the business. It hits 139g/km in manual form, but 147g in this DSG version.
Alfa's Mito is also a relatively conventional hot hatch, and has the innovative Multiair engine. Just 1368cc, it produces 133bhp and emits 129g/km of Co2.
In the cars
You sit low in the Honda, and it's spacious up front. But there are restricted views over the shoulder and behind, and the rear seats are useful for luggage only in reality.
The engine's eagerness, the short-throw shift, the sporty driving position and a firm ride all encourage spirited driving, as does the limited roll, plentiful grip and steering that's quicker than the Insight's. The chassis, though, is still disappointingly inert.
On a B-road it is mildly entertaining, even if its performance rarely rises above brisk. The real fun is to be had from its instrumentation, and the miserly games they allow.
The BMW also allows numbers games - albeit via an old-school, needle-swinging econometer. But the real fun comes from the surprisingly strong performance - determined acceleration comes from 280lb ft of torque that overcomes the tall gearing.
The BMW needs pushing hard to bring it alive, but it achieves its pace with civility, the well insulated cabin giving a premium aura that neither the Mito or Honda achieve.
The Golf GTD is also civilised, and fun. Press the Sport button and it's quick (0-62mph in 81.sec) and handles B-roads with aplomb.
The Alfa is the cheapest car here, and it's better for having the Multiair engine, which is refined and fun. But that sophistication is undermined by a crashingly turbulent ride, somewhat crude handling and weirdly springy, if quick, steering.
Throw in a mushy gearchange, a not-really-premium dash and hard-to-read instruments and you have the least polished vehicle here, by some margin. The Cloverleaf remains the Mito to have.
The Mercedes is as surprising as the name is long. The powertrain delivers the kind of zest you'd expect from an engine 800cc larger. True, its 0-62mph time is the longest here, but on the road its low-revving, steam-train torque and smooth delivery are beguiling.
This dynamism blends with the usual subtle Benz attributes of no-nonsense comfort, space, practicality and aura of robustness.