Precious stuff, diesel. It’s the black gold that we put in our tanks, or at least that’s what it ought to be called as the digits on the filling station pump whizz round faster than a Lewis Hamilton practice lap
So it is galling that we find ourselves using so much of it. There seems to be an inevitable gulf between a typical car’s average fuel consumption shown in the official combined figure, and the economy most of us actually get in real life driving. Economy matters, particularly in challenging economic times such as we’re currently living through. Every little helps, as the saying goes, and squeezing out a few more miles for every high-priced gallon can help ease the burden of motoring costs. It’s good for the planet too, because the close relationship between mpg and CO2 output means that by lowering one, you simultaneously reduce the other.
Cue two days of masochistic driving, otherwise known as the ALD Automotive-Total Excellium MPG Marathon. This annual event pits economy-minded drivers and their cars against one another in pursuit of the frugal motoring Shangri-la of minimal consumption. This year’s event had a special pertinence, given the way fuel prices have rocketed and the motor industry’s current obsession with varying shades of green. Fellow competitors even included a pair of Cornish police driving instructors in a ‘jam sandwich’ Ford Focus Estate, on a mission to cut their force’s £2.3 million annual fuel bill.
Achieving good fuel economy obviously starts with the car you choose to drive and how well it is maintained. But modifying your driving style really can trim fuel bills. So it can certainly pay to adopt eco-driving techniques. If everyone did, the savings multiplied on a national scale would be huge. Research by the Energy Savings Trust and British School of Motoring came up with the startling conclusion that if all drivers across the UK changed their habits to drive more economically, it could cut the combined fuel costs by almost £6 billion, and at the same time reduce CO2 emissions by 10.3 million tonnes annually. There’s fuel for thought!
So there I was in thin-soled shoes, with minimal luggage, and a steely determination to do my modest bit in the cause of fuel preservation. For optimum economy, my MPG Marathon car was a small, modestly powered diesel, a Vauxhall Agila 1.3 CDTi 16v. I hoped it stood a good chance of achieving the lowest overall mpg. It is frugal, with a combined fuel figure of 62.8mpg, and clean, with a CO2 output of 120g/km. Its power output is 74bhp and the torque peaks at 140lb ft. It can accelerate to 62 mph in 13.9 seconds, but with obsessive fuel anorexia, I obviously wouldn’t be going anywhere near that.
THE KEY TO SUCCESSFUL ECONOMY DRIVING IS PIN-SHARP ANTICIPATION AND PLANNING
My secret weapon was co-driver Andrew Duerden, an engineer and Vauxhall’s resident economy guru. Both he and I are past economy run winners, so together we aimed to substantially improve on the Agila’s official figure, with a goal of pushing our mpg up into the 80s. We applied the 5 P’s, as the military would say: Prior Planning Prevents Poor Performance. The Agila was freshly serviced to optimise its running health, and freshly valeted to avoid even the very minimal drag of grubby bodywork. Tyres were pumped up to optimum pressures, so that rolling resistance wouldn’t be hindered by soft rubber. Nothing we didn’t absolutely need was on board, minimising extra work for the engine in pulling unnecessary weight. We kept the windows tightly shut to avoid drag. Radio silent, heater and air-conditioning off, all non-essential electrical items extinguished – we did anything we could to ease engine load.
Light-soled shoes give better sensitivity on the pedals and help soften your demand on the throttle, so that’s what we wore. The knack is to drive as if an egg that you mustn’t crush is balanced on the pedal. Truly obsessive eco-drivers go bare-footed to achieve the lightest possible touch on the throttle, but we considered that a step too far on cool autumn days with the heater switched off. The key to successful economy driving is pin-sharp anticipation and planning. You aim constantly to position the car so that you can see as far ahead as possible. By ‘reading’ the road, you can keep a flow to your driving and judge how to maintain momentum and minimise the need for braking.
Your constant aim is to gauge arrival at junctions and roundabouts so that your way through them is clear. You must contrive to reach traffic lights when they’re at green, and arrive at hazards when they’re empty of other traffic. You make use of downhill momentum to carry you as far uphill as you can manage with minimal throttle. The brake pedal is the enemy, because it squanders momentum that you’ve expended power and fuel to build up.
It was very helpful to have the Agila’s rev counter in its dash-top pod, and an instantaneous mpg read-out on the dashboard computer. We used them to judge gear changes at between 1,800 and 2,000rpm, within the engine’s torque peak, while constantly striving to keep the instant fuel figure as near as possible to the maximum 99.9mpg. The Marathon took us from Bristol, across the Severn Bridge into Wales, up to Macclesfield for an overnight stop, before snaking south again towards the finish back in Bristol. It was a gruelling, energy sapping 411 miles of intense concentation, and at the end of it I was pretty pleased with our 83.98mpg, showing an improvement of more than 20mpg over the Agila’s official figure.
In previous years, that would have been enough to win the event, but particularly intense competition this time meant that we only came fourth out of 39 competing vehicles for best mpg. Amazingly, the top eight cars all managed over 80mpg. What Diesel colleague John Kendall did remarkably well in a Citroën Nemo Van 1.4 HDi, returning the best result among the vans with 84.09mpg.
MEMO TO SELF: must try harder next year. But it just goes to show how well you can eek out a diesel car’s economy if you really try.