How to save fuel and get the most kilometres out of your tank

Every time there’s a fuel price hike (which is often, notwithstanding this week’s price cut), my e-mail inbox tends to get bombarded by fuel-saving tips from various automotive companies.

One tends to ho-hum through these missives as they usually spout some desperately obvious advice on how driving slower or switching off the aircon will save you money at the fuel pumps.

But just how much fuel can you realistically save by driving as if there’s an egg under the throttle pedal?

I got the chance to find out while taking part in a fuel economy run hosted last week by Ford, as part of a group of motoring journalists who were set loose on Gauteng’s roads in a fleet of Fiesta 1.5 diesels.

Motoring journos aren’t by reputation the most economy-focused drivers, but there’s nothing like a bit of rivalry to stir one’s competitive side — even if it means finding your inner granny driver. And so the roads north of Pretoria and the Hartebeespoort area were visited upon by some very conservatively-driven Fiesta 1.5 TDCis last Thursday.

Result? The worst fuel consumption recorded in the test was 4.4l per 100km and the best was 3.2l (Ford’s factory-claimed figure is 3.3l). Admittedly we drove like we were on Valium and also sweltered in the summer heat with aircons switched off and windows closed, and that 3.2l figure won’t realistically be achievable in normal driving.

But, apart from identifying the Fiesta TDCi as one of the country’s most frugal cars, the exercise demonstrated how much fuel can be saved by adjusting one’s driving style. This includes selecting higher gears as quickly as possible to keep the engine revving low, avoiding harsh acceleration and braking, and trying to time traffic-light changes so that you don’t need to stop.

The difference between a fuel consumption of 4.4l and 3.2l per 100km amounts to a range of 954.24km versus 1,313km on the Fiesta’s 42l tank. At today’s 50ppm diesel price of R16.12/l it will therefore respectively cost you R70 to travel a distance of 100km, versus R51.

That’s a notable difference. Multiply that by driving 15,000km in a year and you’ve saved R2,850. That might just be worth driving slower or turning off the aircon.

And please take my advice: in your quest for lower fuel bills stay away from those magical “fuel-saving” devices, such as fuel additives, or magnets that clamp to the vehicle’s fuel line. I’ve tested a number of these snake-oil products and have yet to find one that works, so don’t waste your money.

Fuel economy is a big competitive advantage in vehicles and motor manufacturers spend gazillions in R&D in a bid to squeeze extra mileage out of every fuel tank, and if there’s a consumption-improving gadget that works you can be sure the factory will make it a standard fitment in the car. 

So, at the risk of sounding desperately obvious, the best way to save fuel is to drive slower and keep the engine revs low, as the vehicle slurps about 25% less fuel when travelling at 50km/h in fifth gear instead of third gear. Not to mention that sticking to the speed limit will also keep those traffic fines at bay.

But marginal gains can also be had by adopting other practices, such as switching off the aircon and cutting the engine when idling for extended periods. Leaving a car idling wastes fuel and pollutes the air, and many modern cars (though not the Fiesta TDCi) have auto-start-stop that switches the engine off when stationary. There isn’t much benefit to cutting the engine for very brief stops, but  three minutes of idling equates to about 1km of driving at 50km/h, so if you’re going to be stationary for a while it’s better to switch off and save.

Also, check the tyre pressures regularly as underinflated tyres have increased rolling resistance, thereby raising fuel consumption. Use the recommended tyre pressures as shown on the inside of the driver’s door or in the owner’s manual. Apart from providing better fuel economy, correct pressures also reduce wear compared to underinflated tyres.