Busted: Petrol Pump Myths

With petrol prices on the rise and predicted to hit the $2 a litre mark, many motorists are desperately trying to squeeze more kilometres out of every drop.

There are standard rules the petrol-saving motorist should always abide by, such as reducing the number of trips you make and cleaning out the car to lighten the load. By leaving those golf clubs and other unnecessary equipment at home, your car will run at maximum fuel efficiency. The most important tip is to chill out in traffic. Hard accelerating and braking uses more fuel than smooth driving. However, there are also a lot of ‘old wives tales’ out there, and some of the petrol pump myths we bust may surprise you.

Find out which tips are true energy savers and which are merely petrol pump myths.

1. Fill up in cool weather
The Claim: Don’t fill up in the heat of the day. Refuel in the early morning or late evening. When the temperature is lower, petrol will be denser and last longer.

False. This is no longer a problem, as fuel density is now regulated by the modern pumps used at the petrol station. Temperature correction regulation commenced in Australia with the introduction of the Trade Measurement (Fuel Measurement) Regulations 2002. According to the ACCC, these regulations were introduced to improve certainty and transparency in the volume measurement of petrol and diesel, so going out of your way to full-up at a certain time is not advantageous at all.

2. Air conditioning vs. open windows
The claim: The temperature’s soaring and you're driving on the highway. With petrol prices north of $1.60/L however, you don’t use the air conditioning because it uses more petrol. Driving with the windows down is the answer.

False. Believe it or not, you won’t be able to cut down on petrol usage by turning off the air conditioning in this highway scenario. The action of opening the windows may create drag and reduce the car’s normal fuel economy. Consumer Reports tested the theory, and found that choosing air or windows didn't make a justifiable difference when driving on the highway. Urban driving, according to the NRMA, is where you can reduce fuel consumption by up to 10% by switching off the air conditioning and opening the windows when the weather is fine.

3. To idle, or not
The claim: After you’ve started your car at home, you realise you’ve left something in the house. It’s best to turn the engine off to conserve fuel, while you run inside for a minute. You’re also better off to turn the engine off rather than leave it idle while sitting in traffic.

True. This one is true. Restarting today’s modern engines when already warm is more fuel efficient. According to website Zero Waste Australia, idling can waste fuel. Switch to ‘park’ if you drive an automatic, suggests the NRMA, or when you are stuck in traffic turn the key to the ‘accessory’ position (not to ‘off’). Vehicles fitted with engine-off as standard typically reduce fuel consumption in urban areas by up to 15%.

4. Best day of the week
The claim: Tuesday is the best day of the week to purchase gas because prices level midweek.

True. Whilst in some other countries, the idea of ‘Cheap Tuesday’ is a myth, this is a reality in Australia. However, Wednesday is looming as a competitor for cheaper prices at the petrol pump so the bottom line is keep an eye on prices and fill up early in the week to save.

5. Over-inflate your tyres
The claim: Going on the more-is-better theory, pumping up your types over the suggested pressure will make your car petrol efficient. This can only improve on the fuel economy you’re currently getting.

False. Aside from giving you a rocky ride, over-inflated tyres negatively affect the resistance between tyre and road so this theory holds no weight. There is a difference however when flat tyres are pumped up to their recommended levels. In this case, your fuel mileage could improve by 3.3%

6. Pump slowly
The claim: If you pump your petrol as slow as possible, you will get more petrol and less air and vapors filling up your tank.

False. Petrol stations are designed to minimize air and fumes going through the pipes and into your car’s petrol tank. If you fill your tank slowly you will still get a full tank, as the same cost as one pumped at a faster speed.

7. Put your car into 5th
The claim: You can optimize your fuel economy on the highway by putting your car into the transmission’s highest gear. This will allow your engine to run at a lower level of revolutions per minute, and use less energy.

True. When your car is driven at the highest gear, your car’s engine speed goes down. This saves petrol and reduces engine wear.

8. E10 Fuel is bad for your car
The Claim: Sure, the petrol is cheaper. However the reason it’s cheaper is because it uses more ethanol than petrol, and this is bad for your car.

False. Unleaded E10 contains a Fuel Economy Formula which is designed to help improve fuel economy by reducing efficiency losses caused by engine deposits and friction. This petrol also uses 10% ethanol which is a cleaner burning, renewable fuel component that helps to reduce Greenhouse gas emissions. In saying this however, Unleaded E10 is only suitable for use in modern knock-sensor vehicles that are 10% ethanol compatible. So make sure you check your car’s compatibility before using the cheaper option.

9. ‘Supermarket’ petrol is different
The Claim: Fuel sold using docket discounts at supermarket chains is not of the same quality as that which you would buy from a dedicated petrol station.

False. According to the Petrol Retailers Association, there is no difference between the standard petrol you buy from supermarkets or franchised petrol stations. In most cases the petrol or diesel is even produced at the same refinery and delivered in the same trucks. The exception to this is specialist fuels, such as Shell’s Optimax and BP’s Ultimate. In their case, the fuel is enhanced with additives, which produce that brand’s particular properties.

10. Higher grade of petrol, better the fuel economy
The Claim: Buying premium unleaded gives you better fuel mileage, even though your car manual recommends regular unleaded.

False. While it’s true that premium unleaded is a higher-quality fuel, it doesn’t mean your car needs it to achieve good fuel economy. Read your car’s manual first before shelling out a premium for premium that you may not need.
With petrol prices going through the roof, it helps to know exactly what is fact and what is fiction with commonly-held beliefs. That way, we can target real savings in day-to-day motoring.