Alfa Romeo‘s baby Mito has claimed leadership of the premium petrol supermini segment thanks to a 98g/km model making use of parent company Fiat‘s Twinair unit.

The Twinair engine is an 85hp two-cylinder unit that is 10% lighter and 23% smaller than a four-cylinder petrol, yet is still claimed to offer similar performance.

While petrol versions of the Audi A1 and Mini One get down to 118g/km and 127g/km respectively, the Mito’s 98g/km gives it a significant advantage in the tax stakes, being £12 per month cheaper than an A1 1.2 TFSI for a lower-rate tax payer.

The two-cylinder unit features a dual-mass flywheel, which reduces vibration from the engine and, Alfa claims, allows the driver to change up through the gears earlier. The firm’s not kidding because the Twinair requires drivers to mentally reset to get the best out of it. Waiting until the engine sounds as if it needs another ratio means you’ve already missed the most economical change-up point, and in the case of first and second gears in particular, you’re likely to be bouncing off the rev limiter imminently. It sounds like it’s at mid-range as high as 4500rpm, and the engine can take changing up a gear much earlier than the driver will think. The gearchange indicator light is an educator rather than a reminder, and the driver must trust the screen rather than their instinct for the most economical return.

The 85hp engine needs working hard to get decent performance, but it is a small engine in a car that’s not that small, so there are no surprises. Acceleration is reasonable if you’re willing to sacrifice economy, but driven lightly, progress is slow.

Although the Mito’s RVs can’t touch the Mini or the A1, the fact that it’s cheaper and more efficient than either gives it a cost per mile victory, with the mid-range Sprint version’s 34.9p per mile figure beating the equivalent Audi by 1.5p per mile and the Mini by 3.5p.

Alfa Romeo Mito TwinAir 85 Sprint
P11D price £14.095
Model price range £12,500-£18,760
Fuel consumption 67.3mpg
CO2 (tax) 98g/km (10%)
BIK 20/40% per month £23/£47
Service interval 18,000 miles
Insurance (1-50) group
Warranty 3yrs/unlimited mls
Boot space 270 litres
Engine size/power 875cc/85hp
Top speed/0-62mph 108mph/12.5secs
On sale July 2012
Score 7/10
Verdict Petrol class-leading
emissions, adequate
performance