Rinaldo Rinolfi, who is one of the fathers of the common-rail diesel, and a true powertrain guru, is someone I trust wholeheartedly when it comes to providing feedback on the future of vehicle propulsion. I recently asked the former Fiat engineer which powertrain he believes is the greenest, most affordable option available today. His rather surprising response was: compressed natural gas.
"CNG slashes CO2 emissions by 20 percent to 25 percent compared with a gasoline engine," said Rinolfi, who is now a powertrain consultant whose focus is CNG and liquid natural gas applications.
Rinolfi reckons that engineers have maximized the savings possible from engine downsizing, turbocharging, variable valve control and direct injection. He doesn’t see any new inventions coming that will squeeze significantly more kilometers out of a liter of diesel or gasoline.
He said the CNG infrastructure is growing in Europe and that modern vehicles using the technology also have a small reserve tank for gasoline that eliminates any range anxiety.
To test what Rinolfi said I borrowed an Audi A3 Sportback g-tron, which is powered by CNG and gasoline, and drove it from Turin to Udine and back, a 1,080km roundtrip that crisscrossed most of northern Italy.
The A3 g-tron's two CNG tanks store about 7kg each, enough for 400km, according to Audi and based on the European homologation cycle. During the test the CNG tanks provided just over 300km, which is a quarter less than promised, but is in line with the current difference between European homologation results and real-world driving.
Audi's data shows that the car should emit 88 grams of CO2 per kilometer in CNG mode compared with 115g/km when running on gasoline, a 23 percent reduction. During my test it cost about 15 euros to cover 300km using CNG compared with 27 euros to drive the same distance using gasoline, a 44 percent reduction. In addition, the engine performed virtually the same whether I was driving with CNG or gasoline. Rinolfi's views on the performance of the technology were verified.
Before beginning my journey, I did some research and found that there were more than 1,000 CNG stations in Italy, including one that was just 5km from my house. I figured that finding CNG stations during the trip wouldn't be a problem. Putting me further at ease was that the A3 was equipped with a feature that would warn me when I was running low on CNG and provide navigation to the closest CNG station.
Although I started my trip with virtually no range anxiety I soon learned that just 37 of Italy's 1,000 CNG station were along highways. Making matters worse was that none of those stations was located along my 500km east-to-west route. As my CNG ran low at about the midpoint of my drive to Udine, I had three options.
1. Drive about 40km more to find the next CNG station on the highway.
2. Get off the highway and start searching for a CNG point, most of which are hidden in smalls town where road signs are optional. Only a navigation system that was given the exact longitude and latitude coordinates could find most of these places without getting lost!
3. Keep driving using the fuel from the gasoline tank.
I picked the time-saving option No. 3 for both legs of the journey, completing the final 240km of each trip using gasoline.