German motorists are eager to convert their cars to run with LPG (Liquified Petroleum Gas) and CNG (Compressed Natural Gas). However, unless your next car purchase comes with the LPG/CNG conversion as standard, you should be careful where you get your car converted, according to TÜV Rheinland. The group issued a note of warning stating that several poorly performed conversions had been detected recently. Aftermarket conversions aren't cheap: LPG conversion costs from €1,500 to €2,500 whereas a CNG conversion can top up to €4,500. Legitimate conversions offer legal certificates when they're completed, and when a "black" conversion is discovered, getting it legalized can cost €1,500. This offsets all potential savings, both in emissions and at the pump.
[Source: Auto News