How much CO2 do cars release?

Answer 1

It varies. A compact car like a Mazda2 gives out about .62 lb/mile of CO2. A hybrid obviously gives out less than most cars, like the Honda CR-Z gives out .58 lb/mile. A luxury car usually gives out much more than cheaper cars, like a BMW 550i gives out 1.1lb/mile and an Infiniti M56x gives out 1.05lb/mile. Oddly enough, minivans tend to give out less CO2 than luxury vehicles, like the Honda Odyssey gives out .92 lb/mile and a Toyota Sienna gives out .96 lb/mi. Unsuprisingly, supercars are the worst in terms of CO2 given out, the Ferrari 458 Italia gives out 1.37 lb/mile and a Bugatti Veyron 16.4 Supersport gives out 2.32 lb/mile (maybe that's how to get 270mph...)! It just depends.

The amount a car gives out is measured by the manufacturers and published as a fixed amount in lb/mile or gm/km after a standard test, which us used in the UK for taxing purposes. In reality the amount of CO2 produced is closely linked to the amount of fuel used, which depends on how the car is driven. An accurate calculation of the true amount of CO2 produced is to allow 3.1 lb of CO2 for every 1 lb of fuel used. Or, 3.1 kg of CO2 for every 1 kg of fuel used (the additional mass comes from oxygen that is taken from the air via an air-filter and chemically combined with the carbon in the fuel during combustion).

A gallon of petrol weighs 7 lb. Thus if we take a Honda Civic and drive it at 60 mph it will do 45 mpg and produce 0.48 lb/mile of CO2. But if we thrash it along so that it does 30 mpg, it will produce 0.72 lb/mile. In either case the CO2 emission depends closely on the amount of fuel used. However any attempt to introduce a carbon tax per litre of fuel has been found to be unpopular politically, and also, the present system of vehicle tax in the UK allows far more money to be collected than any proposed level of carbon tax would raise.