What you should know about saving fuel.

This article was first published in the fourth-quarter 2012 edition of Personal Finance magazine.

When someone asks my advice on buying a car, questions about fuel consumption and a vehicle’s fuel-efficiency always come up.

Let me just say that once your kids start driving, this becomes the most important question. If you spend R500 a week on fuel, your son or daughter has the ability to spend 10 times that.

Buying a fuel-efficient vehicle is one way to cut your consumption, but most of your saving will result from how you drive. You cannot drive like Lewis Hamilton and expect your fuel consumption to be the same as the manufacturer claims it will be. Even if you do drive carefully, you shouldn’t expect your fuel consumption to match the manufacturer’s claims. Those claims are based on cars driven at the coast at speeds that would embarrass Miss Daisy.

So, what is the fuel-savvy way to drive? No harsh braking or quick take-offs from stop streets or traffic lights. Dicing with that blonde in the car that pulls up next to yours can only end badly and will increase your fuel consumption.

If you drive with your foot flat on the accelerator all the time, you can’t expect the car to perform as per the manufacturer’s claim or even close to it. When driving on the open road, try to maintain a constant speed. It also helps to adhere to the speed limit.

Motor vehicle manufacturers spend millions of rands on research and development, so when some salesperson spins you a yarn about devices that will lower your fuel consumption, please tell them to get lost. Don’t you think that if there was a way to save fuel, the designers and engineers of these motor vehicles would have thought of it?

Not only will you not save fuel, but if your vehicle’s original wiring harness or spark plugs have to be tampered with to fit one of these “fuel-saving” devices, you will also lose your manufacturer’s warranty. You will do far better if you make sure your tyre pressure is correct and your vehicle is serviced according to the manufacturer’s maintenance schedule.

A stop-start system is now used in most hybrid cars. It ensures that no fuel is burnt when an ordinary car is idling. But if you don’t have a stop-start system, can you just switch off your engine while you wait a robot and hope to save petrol or diesel?

First, if you do that with cars that have not been fitted with a stop-start system, the cost of replacing starter motors and ignition switches would never justify whatever little fuel you save. And unless you are stationary for more than about five minutes, the fuel-saving will be negligible.

Here are my replies to some questions that motorists commonly ask:

* What about tyres? I have heard that they make a difference. Also, will I use more petrol if I have mag wheels? Yes, keeping your tyres at the correct pressure will reduce the drag on your vehicle, thus decreasing fuel consumption.

Please remember that the tyre size (or sizes) that is standard for the make and model of a vehicle has been tested to provide the optimum fuel usage for that particular vehicle. If the tyres are changed to a size that is larger or wider, the resistance increases, which will result in higher fuel consumption.

* While I am waiting at a traffic light or stop street on a slight incline, I keep the clutch and accelerator pedals in balance for a smooth take-off, but my dad says this wastes petrol. Is he right? I cannot for the life of me understand why anyone would play with the clutch and the accelerator to hold a car on an incline. This can only result in excess wear on the clutch and increase the fuel consumption. When you start paying for your own vehicle repairs, then you can play with the clutch. In the meantime, give your dad a break and drive properly.

* Should I keep the petrol tank fairly full to prevent evaporation? Don’t I lose more fuel when the tank is close to empty? The simple answer is no. Fuel evaporation is not a common reason for excess fuel usage. It does not matter whether the tank is full or close to empty, because tanks are pretty well sealed to prevent evaporation.

* Is it true that dirty oil and air filters can contribute to fuel wastage? The air filter in your car is similar to your lungs – it allows your car to breathe. When it is blocked or dirty, your car has to work harder to get air into the system for combustion to occur, and this increases fuel consumption drastically.

Dirty oil increases the friction inside your engine and can cause engine damage. Increased friction means more fuel consumption.

* Does using my air conditioner add to the amount of petrol that I consume? Unfortunately, yes. If you are anything like me, the air con needs to be on all the time in summer and occasionally in winter to demist the windscreen. It does increase fuel consumption, but I think the benefits far outweigh the higher fuel usage.

Driving with your windows open increases your fuel consumption more than does driving with your air con on.

* What about extra weight and drag? Does it make a significant difference if I travel with an extra 20 or 30 kilograms of junk in my car? Do surfboards or roof racks add to petrol consumption? Let me deal with the question about extra weight first – no, not your wife, but the stuff you feel you must keep in your vehicle all the time, when in fact you could just leave it at home. Extra weight, no matter how little, significantly affects your fuel consumption. The heavier the vehicle, the harder the engine has to work and the more fuel it has to consume. So carrying around extra baggage, as in life, is not good for you, the vehicle or your fuel bill.

Now the question about drag. When you put roof racks and surfboards on the car, the entire shape of the car changes, and so does the drag on the vehicle. Hence an increase in fuel consumption.

* I save petrol by freewheeling down hills and coasting into the queue of vehicles waiting at the traffic lights ahead of me. Is it dangerous to put my car into neutral and use its momentum or gravity to keep me going? I would like to believe that you are saving an enormous amount of fuel by freewheeling or coasting, but your fuel-saving is negligible (unless you coast for long distances). However, there will be more wear and tear on the brake pads, and you need to weigh up the cost of replacing the brake pads more often than normal with the money you will save on fuel. As for its being safe, if you don’t run into anyone, I am sure you can continue with your freewheeling ways.

* Do vehicles become significantly less fuel-efficient as they age or does this happen only if I do not maintain the vehicle properly? I like this question – it is a double-edged one. In certain respects, age does not matter significantly if the car is serviced regularly. More mileage will result in higher fuel consumption, due to normal wear and tear – but not as much as you would think.

However, if you have neglected maintenance and suddenly wake up and start servicing your car, don’t expect your fuel consumption to improve significantly, because you will also have to fix all the relevant things that have been damaged. All the car’s moving parts, such as the pistons and cylinder balls, would have been negatively affected while you were not having the oil changed regularly.

Good maintenance has got to be the most important requirement for keeping your fuel consumption consistent and efficient.

You need to service your vehicle more frequently as it gets older, by which I mean if it has done 150 000 kilometres or more. If the manufacturer says you must service your vehicle every 20 000 kilo-metres, then halve that interval for an older car. The least that needs to be done at the service is to change the oil and the filters, and this will cost a negligible amount to keep your car in top shape.

As a man, asking for directions when I am lost is not uppermost in my mind, so when vehicle navigation systems were introduced, I dashed out and bought one. These devices tell you the quickest route to your intended destination – and not getting lost automatically contributes to saving fuel.

* Sagie Moodley owns Sagie’s Auto Performance, a workshop in Midrand. He is also a talk-show co-presenter on 567 CapeTalk and 702 Talk Radio.