Six fuel saving strategies that are a waste of time

As South Africans look to save every cent they can on fuel, certain myths have crept into society. Will these six myths save you money or are they just a waste of time?

The South African economy showed some signs of improvement in 2025, but fuel remains an expensive commodity. At more than R20 a litre whether you are using 93 or 95 petrol or one of the various grades of diesel, fuel makes up a significant portion of the monthly costs of owning and driving a vehicle in South Africa. Fuel is also a significant cost contributor to holiday travel over the Festive Season.

Premium grade will make your car lighter on fuel

Many people believe that using premium fuel, such as 95 when filling up at inland pumps or low sulphur diesel, improves engine power and efficiency, but this is not true.

If your car was not designed for it, paying the extra amount for premium fuel will offer no benefit to your car. It won’t perform better, get more mileage, go faster or run cleaner. Paying for premium fuel when your car is built for regular fuel will only benefit petrol companies.

If your car manufacturer recommends using premium fuel, then you should stick to the manufacturer’s guidelines. This is usually the case with high performance turbocharged cars. Using a lower grade of fuel in these vehicles will affect performance and can clog up emissions devices such as catalytic convertors and particulate filters. In summary, use the grade of fuel that the vehicle manufacturer prescribes.

Warm up your car before driving

Years ago people believed that your car would use excessive amounts of fuel if you didn't warm it up before you started driving.

While older engines took longer to warm up, modern engines can reach operating temperature in 20-30 seconds. This means that you can get into your car and drive off immediately, but it is a good idea to drive sedately for the first few kilometres, before accelerating heavily.

In short, don't waste petrol warming up your car’s engine, you will save more by minimising the time spent idling.

You’ll get more petrol if you fill up in the morning

The theory says that petrol expands at higher temperatures and becomes denser in the cold mornings, so if you fill up your petrol tank on a cold morning, you will get more fuel for the same money since the quantity of fuel is measured in litres rather than kilograms.

However this is not true as the fuel reservoirs at petrol stations are designed to minimise temperature fluctuations for a variety of reasons. The tanks are encased in concrete to avoid heat conduction. So no matter the outside temperature, the temperature and quantity of the fuel will stay relatively constant. In addition modern fuel pumps are extremely accurate and regularly calibrated, so one litre will be one litre, no matter what time of day it is dispensed.

Letting your car idle is more fuel efficient than turning it on and off

It is an old myth that restarting your engine consumes more fuel than letting it idle for several minutes.

This might have been true in the case of old engines that used carburettors, however newer engines that use direct or electronic fuel injection are more intelligent than that.

In modern cars a few seconds of idling uses more fuel than turning your car off and on again. Manufacturers actually leverage this fact to save fuel as most modern cars are now equipped with stop/start technology where the vehicles engine will automatically switch off when you stop at a traffic light and then restart as soon as you press the accelerator to pull away.

Smaller cars are more fuel efficient

Many people believe that a cars size is directly related to its fuel consumption and that smaller cars will naturally be lighter on fuel. While this may have been true some years ago, advances in vehicle technology and efficiency mean that a car’s efficiency is no longer only affected by its size and weight.

In addition when fully loaded the engines of smaller, lower powered, cars will need to work harder in order to maintain the speed limit. A larger more powerful car will be less stressed and could be lighter on fuel.

Manual cars are more efficient than automatic cars

This is another fact that might have been true decades ago, but which is no longer valid. Advances in automatic gearbox technology and the development of gearboxes such as CVTs and dual clutch automatics mean that automatic vehicles are now as efficient as manual vehicles. An automatic vehicle may even be more fuel efficient as it keeps the vehicle in the sweet spot in terms of performance and fuel efficiency and offers more gears, which results in a lower engine speed when cruising.

What can you do to save fuel?

One of the easiest ways to save fuel is to ensure that your car is properly maintained as this will help your car achieve its optimum fuel consumption. Driving with a dirty air filter can increase fuel cost by up to 13% and incorrectly inflated tyres can have a big impact.

However, the biggest impact on a vehicles fuel consumption is the driver. Smooth driving while avoiding unnecessary acceleration and sticking to the speed limit will save more fuel than any other fuel saving strategy could ever get close to.