VW has updated the compressed natural gas-powered TGI versions of the Polo and Golf with a third natural gas tank for a longer driving range in pure CNG mode.

The new Golf TGI now comes with a total tank volume of 115 liters (17.3kg), which makes it capable of driving up to 422km (262 miles) on CNG according to the latest WLTP standards.

As for the Polo TGI, which is powered by a three-cylinder 90PS 1.0-liter unit, the additional tank extends the volume by 16.5 liters for a total of 91.5 liter (13.8kg), meaning that CNG-only range is now up to 368 km (228 miles).

The VW Golf TGI is powered by a turbocharged 1.5-liter four-cylinder that runs on the Miller cycle and has a compression ration of 12.5:1. The turbocharger features variable turbine geometry for more power in the lower rev range. It produces 128hp (130PS) and 147lb-ft (200Nm) of torque and is paired to a dual-clutch transmission, while CO2 emissions are 98-95g/km.

Both TGI models come with a backup petrol tank with a smaller volume. One of the key benefits of having a car that runs on compressed natural gas (CNG) is the lower fuel prices: in Germany the cost saving compared to diesel is 20 percent, or 40 percent if compared to petrol.

In addition, driving on CNG produces around 25 percent less CO2 emissions than petrol and its exhaust gases contain significantly lower levels of carbon monoxide and nitrous oxide (NOx).