fuel emissions

[wopshistos]

I have a car that does 40mpg and the registration document says it produces 225 g/km CO2. If the weight of fuel over the kilometre is around 50g, I produce CO and unburnt lean fel where is the weight coming from?? Petrol is around 85% carbon and weighs say 800g/cc. Oxygen and carbon aen't too far away in terms of atominc mass.

[jake-the-peg]

40mpg is about 14km/l or 0.07l/km which is about 52g of fuel per Km

CO2 has a relative atomic mass of 12 + 2*16 =44 so your output is 225 * (12/44) = 61g /km

So there's a discrepancy of about 20%

Is that the same discrepancy as you calculated or did you miss the second oxygen?

All the same there is a discrepancy - I doubt the hydrogen and the other additives
would make that much difference - I wonder whether the car produces 225g *at* the
same speed as it does 40mpg.

Are you taking both figures from the manufacturers literature or are you mixing your milage
figures with the manufacturers'?. It may be that they are over estimating the CO2 figures a bit
the way that speedometers are set to overread

[ABerrant]

Typical 'stated' fuel consumption figures for cars rated 225g/km CO2 are of the order:

Urban Fuel - 20 mpg
Extra Urban - 40 mpg
Combined - 30 mpg

http://www.carpages.co.uk/co2/

[Teddio]

A quick calculation: Assuming petrol is pure Octane, 114g of petrol will produce 352g of carbon dioxide and 162g of water.