Petrol prices have recently reached levels not seen for some years, and with many cars also no longer able to use the entry-level E10 fuel filling up can induce a nasty shock to the wallet. Most modern cars do their utmost to save fuel whenever possible – stop-start systems, cylinder deactivation, drag reducing active aerodynamics – but the weak point, as usual, remains the biological system behind the wheel.
However, there are a number of fairly simple changes any of us can make to reduce costs and of course emissions without resorting to joining the cult of the hypermilers. And with energy prices rising as well, many of them will apply equally to EVs.
By act we mean car, and by clean we mean, well, clean. Manufacturers spend millions of pounds and countless wind tunnel hours perfecting the airflow over and around their cars in order to maximise efficiency. A coating of dust, mud, bird droppings and bug graveyards are going to interrupt that smooth airflow and each little bit adds up. Frequent cleaning and waxing will help maintain a smooth profile.
This is actually a bit of a contentious one since using air conditioning does increase fuel consumption by up to 10 per cent according to the AA. However, opening windows increases drag which also raises consumption. The best approach is to open all the car’s windows when you first set off to clear the hot air inside it quickly. Open windows are best at around town speeds but on dual carriageways and motorways switch to air-con as the most efficient option.
Post-Christmas we’ll probably all be considering weight loss measures but for better fuel economy it really is important to ditch the junk in your trunk. I know full well there are several miscellaneous items including car parts, cleaning kit and half empty water bottles that I am needlessly driving to and fro on a daily basis, and I suspect most of us could say the same. I’m not sure it’s exactly what Colin Chapman had in mind when he espoused ‘adding lightness’ but it definitely helps.
We’ve already mentioned reducing drag in terms of car cleaning and windows open versus closed but the biggest impact comes from items such as roof bars, boxes and even those little football supporter flags affixed to the outside of your car. According to the Energy Saving Trust an unused roof rack increases drag by 16 per cent at motorway speeds while an empty roof box ups that to 39 per cent.
Both under and over inflated tyres can adversely affect fuel consumption according to the RAC with the latter being a particular problem as it increases the contact area of the tyres on the road, upping rolling resistance. You should also adjust the pressures according to the load in the car, as there is a significant difference between solo journeys and a full family road trip. Regular maintenance and servicing will likewise help keep consumption down.
Any racing driver will tell you that anticipation is a key component in carving one’s way through the field and the same principles apply in achieving award winning mileage. Lifting off the accelerator in order to time your arrival at a roundabout perfectly, proceeding without stopping, is not only frugal but incredibly satisfying as well. Keep the car in gear however, as modern ECUs automatically shut off fuelling when coasting but the same doesn’t apply when in neutral.
Clearly the faster an engine turns the more combustion cycles it completes and therefore the greater the fuel consumption. The best approach is to accelerate smoothly up to around 2,000rpm before changing up into the next gear and once at a steady speed keep the car in the highest possible gear. Don’t take it too far however, pushing the accelerator too far in too high a gear will leave the engine labouring and demanding more fuel from the ECU in order to prevent stalling.
Engines work most efficiently when warm so a bit of planning to cover off all your weekly errands in one trip will pay dividends. Google Maps recently rolled out an Eco Route option in the US where it estimates it could save 1 million tons of carbon emissions per year. Doubtless this will be coming to Europe soon to make fuel consumption-friendly route planning a lot easier.
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