SAVING FUEL: The Motor Industry Workshop Association lists fuel-efficiency myths in SA. Image: iStock
Cape Town - Fuel-efficiency is always a hot topic and for decades there have been myths regarding fuel consumption.
Vishal Premlall, director of the Motor Industry Workshop Association (MIWA), says while fuel-efficiency tips may have worked in the past where vehicles had less sophisticated components, most don’t apply anymore since vehicles manufactured today have computer-controlled automotive systems.
He says: “Fuel efficiency is, however, still a consideration. Fuel is not cheap and many people spend a larger portion of their salaries each month on fuel to commute."
Interestingly, he believes that the most fuel-efficient engines currently in SA are diesel units.
He adds: “Diesel engine technology has progressed in leaps and bounds over the past decade and most certainly in the last five years, proving that this technology is becoming the one of choice.
"European countries are, by far, at the forefront of diesel powered use and the rapid expansion will see diesel powered passenger vehicles become the vehicle of choice in the near future probably surpassing all other forms of power. However, since only a few vehicles models currently have diesel engines, it’s probably a good idea to know the truth about many fuel-efficiency tales out there."
Here are six important fuel facts you should know: List by Miwa
1 Gearing into neutral when your vehicle is stopped
Miwa: "This idea may have been relevant when engines used carburetors but today’s cars have computerised fuel-injection systems. These systems sense if an engine is revving above idle when you ease off the accelerator. If that happens, the fuel injectors shut off, so fuel is no longer injected into the engine, even if the car is still in gear. By constantly shifting in and out of neutral the only thing you may accomplish is premature wear on your gear box."
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2 A full tank is more fuel efficient
Miwa: "The idea that a tank more full than empty will prevent fuel evaporation inside the tank is incorrect. Fuel systems in modern cars are designed with vapour recovery systems so no evaporation is possible. Some vehicles with pressurised fuel systems even display a ‘check engine’ light if the petrol cap is loose, missing or not properly sealed."
3 A dirty air filter leads to lower mileage
Miwa: "The engines in older vehicles pulled air straight through the air filter into the carburetor, so a clogged filter could affect fuel efficiency to some degree. However today's advanced engines have a computerised engine control module (ECM) to regulate the air-to-fuel ratio.
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"Air goes through the filter and then through a mass airflow sensor that lets the ECM gauge the airflow and adjust the fuel accordingly; less airflow means less fuel is sent to the engine. While fuel efficiency may not be affected, dirty air filters can lead to sluggish acceleration."
4 Filling up when it’s cooler saves me money
Miwa: "For years, a myth has been circulating that if you buy petrol during the cooler part of the day you get more for your money, since a cooler liquid is denser. This theory may sound believable but at filling stations petrol is almost always pumped from storage tanks underground that are naturally insulated from large temperature swings. Because of this, any slight change in the temperature of the petrol is so small you wouldn't notice any real savings."
5 Cruising downhill in neutral saves petrol
Miwa: "This is one of the biggest myths thrown around. The truth is that when coasting in Neutral, the engine is idling, consuming just as much petrol as when it's idling at a traffic light or warming up in your driveway."
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"The reality is that it’s actually a bad idea to roll downhill or up to a stop sign in neutral because you need to be able to use the accelerator to avoid any unexpected road hazard. Cars don't handle well in Neutral during sharp cornering maneuvers when the engine isn't connected to the drivetrain - the components in the vehicle that generate power."
6 Fuel saving devices
Miwa: "Lastly be aware of claims made by manufacturers regarding fuel saving devices. There are a number of different devices doing the rounds and each one is purported to have magical fuel saving powers, be it a magnet device connected to the fuel supply line which “aligns” the atoms in the fuel by electromagnetic field, to the swirl or vortex device which is fitted to the intake manifold. There is no scientific evidence that any of these devices will in any way improve the fuel efficiency of a motor vehicle. Be cautious of marketing ploys and before you consider purchasing such a device, seek the expertise of your nearest Miwa dealer to guide your decision making."
Premlall says the rule of thumb is, if it sounds too good to be true, it probably is!
He concludes: “Many a gullible consumer has been duped into doing costly damage to their vehicle by the unscrupulous marketers of these devices. If in doubt, rather ask an expert."