Well, that concerns only consumption.

In Europe it is different in each country, but for example in Belgium...
when you register a new car: http://www.moniteurautomobile.be/page.cfm?titre=InfosServices&page=TaxesNewCar.h- tm&texte=1546&col=N&ToolbarSelect=InfosServices_Taxes
when you register a not-new car: http://www.moniteurautomobile.be/page.cfm?titre=InfosServices&page=TaxesOldCar.h- tm&texte=1546&col=N&ToolbarSelect=InfosServices_Taxes
What you pay each year: http://www.moniteurautomobile.be/page.cfm?titre=InfosServices&page=Taxescar.htm&texte=- 1546&col=N&ToolbarSelect=InfosServices_Taxes
My Peugeot 206 with its 1.4 75hp engine is in the first category, up to 8 CV (it is 55 kW).
If you take for example a Corvette C6, for the first registration you pay nearly 5000 €, and then 2500 € per year as tax!
The first one is due to the number of kW/hp, as for example a 2-liter 247hp Lotus Exige Cup 240 pays the same; but the second one is due to the engine size only if I am correct, as then the Lotus only pays 270 € per year.
Lots of old (and less old) US cars with big engine used LPG, as the annual tax was then divided by 10.