The Audi A3 G-tron is another example of Audi's commitment to developing alternatively fuelled cars.
In most ways, the G-tron is identical to any other A3 Sportback 1.4 TFSI. However, its engine has been modified to run on compressed natural gas (CNG) as well as petrol.
The G-tron runs on gas most of the time, automatically switching to petrol when the CNG tank is empty although the switch can be made manually if required.
Unlike the electric A3 E-tron, the CNG-powered G-tron will not be coming to the UK, although it will go on sale in Europe at the end of the year.
Whats the 2013 Audi A3 G-tron like to drive?
Our brief test drive around Berlin wasn't ideal, but gave us the chance to see how the G-tron handled stop-start traffic and the occasional burst between traffic lights.
The G-tron will be available in the same trims and suspension set-ups as the standard A3. Our test car was a Sport model, which means it had slightly stiffer suspension than our favourite version, the SE.
As a result, the ride was a little fidgety over broken surfaces, but improved considerably with speed.
The steering is just as precise and accurate as it is in regular A3s, and although the G-tron is 60kg heavier than the standard car, body control and turn-in dont feel compromised.
There are downsides to CNG power, though. The G-tron feels decidedly flat lower down the rev range, and doesn't start to pull hard until around 2500rpm.
The G-tron is 11bhp down on the petrol 1.4 TFSI A3, making it around 1.5 seconds slower to 62mph.
When running on gas, the G-tron has a coarser engine note, which is transferred to the cabin more readily.
Switch to petrol power, though, and things are much better.
Whats the 2013 Audi A3 G-tron like inside?
From the driver's seat, all that distinguishes the G-tron from a regular A3 Sportback is the CNG fuel gauge.
Otherwise, it's business as usual, which means the A3's interior is classier than any other small family car's. The materials are as plush as those you'd find in an executive saloon, and the assembly is close to flawless.
The latest version of Audi's MMI infotainment system comes as standard. This has the usual rotary dial that Audi drivers will be familiar with, but the shortcut buttons have been replaced by raised toggle switches, which are easier to find at a glance.
Finding a comfortable driving position is also easy because there's loads of adjustment in the seat and steering wheel.
Granted, rear space is a little tight, but two six-footers will still fit comfortably. Access isn't bad, either.
The standard A3's boot is one of the biggest in the class at 365 litres. Unfortunately, the intrusion of the CNG fuel tanks means the G-tron loses its spare wheel compartment, although the main loadbay is virtually the same size as the regular car's.
Should I buy one?
You can't at least not if you live in the UK.
However, in mainland Europe, where CNG is readily available, the G-tron will make sense for some buyers, simply because gas is significantly cheaper than unleaded petrol.
Prices haven't been confirmed, but the fact that Audi has funded the research and construction of its own gas plant suggests it's confident about the G-tron's success.
That said, a 1.6-litre diesel A3 is almost as clean (emitting 99g/km of CO2) and offers stronger, more flexible performance.
Engine size 1.4-litre turbo petrol
Price from n/a
Torque 148lb ft
0-62mph 11 seconds (est)
Top speed 118mph
Fuel economy 3.5kg CNG/100km
CO2 95g/km (est)