AS A car owner you’ve probably heard your fair share of fuel-efficiency tips, but have you ever

questioned whether they are in fact true or merely myths?

Les Mc Master, chairman of the Motor Industry Workshop Association (MIWA), said there are

many fuel-efficiency myths doing the rounds in South Africa currently, especially following the

recent truck and taxi accidents that have made headlines.

“The fact is that many fuel-efficiency tips may have worked in the past where vehicles had less

sophisticated components. Most of these don’t apply anymore

since vehicles manufactured today have computer-controlled automotive systems. Some of the

tips didn’t even make that much sense in the past, so as a vehicle owner you need to be savvy

about the tips you receive and rather ask an expert if in doubt,” said Mc Master.

Based on tips from MSN Autos (https://home.autos.msn.com/), Mc Master offered his advice on

these fuel-efficiency myth busters:

Gearing into Neutral at stops

THIS myth may have been relevant when engines used carburettors, 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.

A full tank is more fuel efficient

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.

A dirty air filter leads to lower mileage

THE engines in older vehicles pulled air straight through the air filter into the carburettor, 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. 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.

Filling up when it’s cooler saves me money

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.

Cruising downhill in Neutral saves petrol

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. 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 an unexpected road hazard. Cars don’t handle well in

Neutral during sharp cornering manoeuvres when the engine isn’t connected to the drivetrain –

the components in the vehicle that generate power.

Fuel saving devices

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. Rule of thumb, if it sounds too good to be true, it probably is! Many a

gullible consumer has been duped into doing costly damage to their vehicle by the unscrupulous

marketers of these devices.