You think this tax on 'gas-guzzlers' is about saving the environment? Think again.
I am taxed for OWNING a car, whether I drive it or not. also, I drive a Chrysler Grand Voyager 3.3 litre V6 - a 'gas-guzzling monster' so I pay tax in band F.
This car has been converted to LPG, last emissions test gave a reading of 0% CO2 (limit 3.5%) and 73ppm Carbon (limit 1200), those reading put it in band A, but as it is not a factory fitted system I STILL PAY BAND F.
I think you're confusing CO2 and CO emissions. CO is the result of incomplete combustion and can be tuned down to practically nothing. LPG is good in this regard because the fuel is of a simple molecular composition and is easy to burn completely.
CO2 is the inevitable product of burning a carbon based fuel in oxygen, and the amount produced is directly linked to fuel consumption (type and quality of fuel are the only variables.) There's no way to tweak it down other than improving the car's MPG figures. A larger and heavier vehicle will always require more power to move it around than a lighter one, so your CO2 emissions will never come close to that of a smaller vehicle.
But you make an excellent point over LPG, which is effectively free fuel at present as it's a natural byproduct of the production of other fuels. What they can't find a use for, they burn off at the stack, which gives us global warming for nothing. When you're running on LPG, your car is not only carbon neutral, it's also wasting none of our valuable natural resources (at least none that we'd be able to stockpile in sufficient quantities to be of any use.)
So where is the 'incentive' that Grabber Brown keeps spouting about?
It's in the duty on the fuel, though as I see it that should be even lower for the reason I've already given. Your road tax for driving a 'hogger' is punitive for political reasons. Like it or not, your lifestyle choice has automatically branded you as frivolous, greedy and wasteful even though you've gone out of your way to be environmentally friendly.
Remember Brown? he's the guy seen on TV last week arriving for a speech about global warming. He arrived in a 4x4.
I'm not sure when hypocrisy became a required character trait for politicians, but it certainly seems to be the norm these days.