First, there's a base tax based on displacement: €2 per each 100 cubic centimeters if it's a gasoline car or €9.5 if it's a diesel car. Additional taxes are based on CO2: for each gram over 120 that your car emits per kilometer, your tax will be increased by €2. That CO2 limit will drop to 110 grams in 2012 and, from 2014 onwards, it will be 95 grams. So, for example, the new Toyota IQ 1.33, which emits 113 gm/km. The 1.3-liter gas engine will be taxed at 13 * 2 = €26 and the number will stay the same until 2012. At that time, its owner will be charged an extra €6 additional (€32 in total) because 113-110 = 3 grams at €2 each. Then, in 2014, the tax will be even higher: 113-95 = 18 grams, at €2 each, €36 additional (€62 total). I'll let you do the math with a Porsche Cayenne S.
[Source: Auto News]
Photo by ckroberts61 under CCL 2.0