Driver Knowledge Tests

How to calculate the CO2 (carbon dioxide) produced while driving

Diesel produces approximately 2.68kg of CO2 per litre, petrol produces approximately 2.31kg of CO2 per litre burned, and LPG about 1.51kg per litre. These numbers are fairly consistent across all vehicles. If your vehicle is passing a lot of unburned fuel out of the exhaust, then the numbers will be different.

How to cut your CO2 production

The more litres per 100km that your vehicle does, the less CO2 it produces. Benchmark fuel economy for cars is now between four to six litres per 100km, but it does matter a lot on your driving style and the type of driving you do. The most fuel is burned while the engine is heating up during the first 10 minutes of a trip, so if you can combine several short trips into one longer trip, it will save you money.

Vehicle technology to support fuel economy is becoming more commonplace.

Auto stop/start – these are systems which automatically stop your engine when you come to a stop then start it in an instant when you either lift your foot off the brake, or put it in gear. It reduces the fuel lost through simply idling, which can be as much as two litres an hour in a car with a large engine, or when the engine of a small car is cold and you are using the air conditioning.

Hybrid vehicles – petrol-electric hybrids recapture braking energy and can switch to electric mode when conditions are right

Plug-in hybrids – pure electric vehicles can be recharged using more efficient forms of energy such as solar, wind and hydroelectric

Twin-charge engines – smaller engines that have both a turbocharger and supercharger can create equivalent power to a larger V6 but with much better fuel economy

Weight and aerodynamic advantages – a lot of the power of the car is used overcoming air resistance and getting its bulk up to speed. The more aerodynamic and the lighter the car, the less the engine has to work.

Darren is an expert on driving and transport, and is a member of the Institute of Advanced Motorists

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