Long posts

How to drive greener

There’s no denying that transport is essential. We need it to get ourselves from place to place, to ensure goods get to where they need to go, and even to transport the fuel that makes transport possible. Transportation based on fossil fuels, such as petrol and diesel, (including planes, trains, cars, trucks and ships) contributed 20.5% of the global Greenhouse Gas Emissions (GHGE) in 2014, making it the second highest contributor after electricity production (49%), with manufacturing and industry coming in close third (20%). Furthermore, personal transport and freight transport are both expected to increase by  1.7% and 2.3% respectively between 2000 and 2050, with the majority of the increase coming from rapidly developing nations.

With alternative fuel source technology still a long way from being mainstream, it’s necessary to look at other ways to reduce emissions from vehicles. In many countries, access to mass public transport allows the carbon footprint to be reduced, but in South Africa, owning and driving a car is largely unavoidable. We have very limited access to reliable public transport and where it does operate, it services a very small area, like the Gautrain or the Cape Town city buses. For the rest, your options are to drive yourself, or to never leave home. But just because you have to drive, doesn’t mean there’s nothing you can do to reduce the impact your car has on the environment. Whether it’s driving more carefully or getting your car serviced regularly, here are a couple of suggestions of ways you can drive greener.

1. Keep your car well maintained

New cars are being built to stricter fuel efficiency regulations, with countries like China, India, Europe and Japan aiming for a minimum fuel economy of of 23 km/litre in all new cars by 2020. But new cars are expensive, and the resources needed to build new cars have other damaging effects on the environment, so it’s better not to buy new unless you have to. Instead, you can invest in keeping your car in good condition and getting it regularly serviced. Some of the easiest ways to do this are:

  • Keep your tyres properly inflated to the recommended volume. Tyres that are too soft have greater surface area in contact with the road and produce more drag, which can reduce fuel efficiency by up to 1.5% per 0.5 BAR (7 psi) under the recommended pressure.
  • Check your air filter regularly to improve your engine’s efficiency. Your car’s air filter removes the particulate matter produce through ignition of fuel. When this is clogged, less air can be drawn into the engine and can reduce engine power and fuel efficiency. (Side note: air filters are usually made of paper and are thrown away when they are replaced. K&N make air filters of greased cotton that last longer and can be washed and reused, reducing waste).
  • Get your car serviced according to the manufacturer’s guidelines. During a service, your car will be checked top to bottom for performance reducing issues, such as worn brake pads, dirty air and oil filters, and thin tyre tread. Keeping these things in good condition can improve acceleration, engine power and braking while driving, which can contribute to up to 4% better fuel efficiency and also improves the vehicle’s handling and safety.

2. Drive more slowly

Reducing your speed by 10km/h can make a surprisingly big difference to your car’s fuel consumption and carbon emissions. At higher speeds, the wind resistance on your car  is higher and requires more energy, i.e. your car uses more fuel. A simulation run by the European Environment Agency, showed that if drivers stuck to a maximum speed of 110km/h on a highway (rather than 120 km/h) it would reduce fuel consumption by 12 – 18% for diesel and petrol cars respectively. This is expected to reduce carbon emissions by up to 25% in petrol engines, and particulate matter (also a hazard for human respiratory systems) in both diesel and petrol engines.

3. Brake and accelerate more gently

This goes hand-in-hand with driving more slowly. Accelerating more aggressively and braking harder will consume more fuel and produce more emissions. The harder you push your car to accelerate, the more fuel the engine burns and the more emissions your car produces. My car (a 2016 model Ford Figo 1.4 hatchback) has an acceleration rate from 0 to 100km/h of about 15 seconds. In other words, I should expect my car to take MINIMUM 15 seconds to reach 100 km/h. If I try to do it in less than that time, I’m pushing the engine too hard. Relatedly, braking hard requires more acceleration to regain lost momentum. Slowly decelerating may mean you don’t have to stop at all, and allows you to maintain momentum, reducing the amount of power and fuel required to get your car moving again. It’s also easier on your tyres and brake pads and keeps your car running smoothly for longer. (See earlier point about keeping your car well maintained).

4. Turn off rather than idling

Idling (leaving your car running while not moving) for more than 10 seconds uses more fuel than restarting your engine. Modern engines are far more fuel efficient at ignition than they used to be, meaning that frequent restarts are no longer bad for your car. This isn’t really an option if you are at a stop street or in traffic, but if you’re waiting for someone or something, it’s almost always better to just turn your engine off.

5. Take the far parking bay

We all know that feeling of hope that if you do one more lap of the parking area you might get a parking right at the door. But multiple circuits of the parking is actually one of the least fuel efficient things you can do. When cruising through a parking area you generally drive slowly and in a low gear (1st or 2nd). Lower gears use more fuel and the more time you spend driving in these gears, the worse your fuel efficiency becomes. So while it might be convenient to park close to the door, it’s better for your car, your wallet and the environment to just take the first parking you find. Plus the walk will do your body good too. (Obviously this does not apply to differently-abled readers who use walking/mobility aides, like wheelchairs or crutches etc.)

6. Keep your revs low (but not too low)

Faster revolutions per minute (rpm) mean that your engine is working harder and using more fuel. As mentioned above, low gears are less fuel efficient than high gears because they require faster engine revolutions (high rpm). Ideally, you should aim to change gears as soon as possible for maximum efficiency. The ‘ideal’ will be different for different cars, but generally, with a manual gearbox you should be aiming to keep your car between 2000 and 3000 rpm most of the time.

However, there is a diminishing return on low rpm, and you can usually feel this as your car may start to feel shaky or you might notice a slight shudder, and a decrease in power. This is also bad for fuel consumption because your engine will be straining to accelerate with very little power. I saw this best explained as similar to trying to pedal a bike with a loose chain. Again, it is different for different cars. My car cruises very happily at 2000 rpm, with me changing up at about 2500 or 3000 rpm, and changing down at about 1500 rpm.

7. Air-conditioner or windows open?

Ultimately the issue comes down to drag vs. engine load. Rolling down the windows reduces the aerodynamic-ness of your car and increases fuel consumption. Using the AC requires the engine to work harder and increase fuel consumption. There seems to be a lot of disagreement on this one. A study by the Society of Automotive Engineers shows that using the AC is always the less fuel efficient option, but then CNN and New York Times have released articles saying that it doesn’t actually make a big difference either way. Still other sources say it depends on how fast you travel which option is better.

I will be honest, the idea of driving on a freeway with the window open sounds awful. Not only would it be noisy, but the volume of car fumes getting in your window would surely not be good for you. So, based on the reading I have done, this is the strategy I have adopted. When I’m driving at 60 km/h or less, such as driving around the suburbs or to the local shops, I open the window. At higher speeds, 80 km/h – 120 km/h, I put on the AC. One tip I have picked up, that sounds useful and plausible, is to open your window and run your car’s fan (not air-conditioner) really high for a few minutes to cool the interior slightly, before switching on the AC and rolling the windows up. This reduces the amount of ‘work’ the AC has to do to cool the car down and can save your engine a bit of strain.

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