Green driving : it’s never too late to learn

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Twenty-two years after passing my driving test, five years after I became interested in green motoring, and 18 hours after arriving in Paris from London, I get my first eco-driving lesson.

Like many old dogs, I think I’ve already learned all the tricks. I know that fuel consumption increases dramatically at the upper end of an engine’s rev range. I know that slowing down and speeding up simply wastes fuel. I know that anticipation and observation are paramount to improving your litres-per-kilometre or mpg score.

So I approach my lesson with scepticism. What can I learn in half an hour that might make any real difference?

I’m wrong, as it turns out. Very wrong.

My instructor plugs his laptop into our specially instrumented Renault Clio Eco2, a 1.5-litre diesel supermini with official combined-cycle emissions of 98g/km and 3.7 litres per 100km (about 64mpg). Then we plunge straight into the Parisian traffic, following a 5km loop of busy urban roads, to benchmark my performance without instruction.

Fifteen minutes later, back at base, the laptop gives the good news. I’ve achieved 5.8L/100km, or just over 40mpg. Not bad for city driving.

I expect my instructor to dissect errors in my footwork or berate my gear changes, but instead he launches into a basic physics lesson – stuff I first learned more than 30 years ago. The principle of conservation of momentum and the effects of gravity, followed by their applicability to Parisian slopes and traffic lights.

Out on the streets again, he launches into stream of directions: choose the queue with the least cars; maintain a steady speed; keep the revs under 2,000; keep the revs over 1,000; go straight from third to fifth as soon as you hit 50km/h; get off the gas downhill; accelerate but watch the revs uphill.

I have trouble with one instruction - braking while still a long way away from a red traffic light. It feels wrong, as if it must be less economical than simply getting off the gas and coasting up to the light and stopping. But early braking means you can prolong your approach, which will often let you avoid stopping altogether. If you are still moving when the light goes green, there are big fuel savings to be had. Or, in physics terms, shedding a little momentum early conserves more momentum later. And so, as I fail to follow instructions by braking with too little force, my instructor yanks on the handbrake. It does the trick. The car slows but doesn’t stop, the light changes, I pass through the junction without having to visit the fuel-sucking realm of first gear.

Back at base for a second time, the laptop reveals the even-better news. This time I have achieved 4.4L/100km – about 53mpg. A whopping 25 per cent improvement.

My instructor asks what my monthly fuel bill is, and then cheekily suggests I give him 25 per cent of that amount as a tip, in part payment for the future fuel savings his lesson will unlock.

I wriggle out of paying, but I can’t avoid looking back over my two decades of motoring. I wonder what 25 per cent of all my past fuel fill-ups might equate to, not just in cash but in thousands of litres and tonnes of CO2.

Lem Bingley is director of content atBusinessGreen.com, a site providing news and analysis for firms interested in sustainable business. He also writes a personal blog, GreenMotor.co.uk, about electric cars, hybrids and fuel economy.

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