Petrol Pump Myth

I have seen a lot of emails circulating around discussing about this with the recent price increment. There are lots of myth about when, where and what are the best petrol pumping practise.

1. Do not pump full tank of petrol

True. Many of us are not aware that the petrol kiosk pump has a return pipe-line (in black ). When the petrol tank (in the car) reaches full level, there is a mechanism to trigger off the pump latch and at the same time a return-valve is opened (at the top of the pump station) to allow excess petrol to flow back into the sump. But the return petrol has already pass through the meter, meaning you are donating the petrol back to SHELL/ PETRONAS/ CALTEX/MOBIL..........

2. Fill up in cool weather - 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.

True in Malaysia. Fuel is denser during cooler conditions. The fuel pump measures the volume of petrol and not the density of the fuel concentration. This would not be the case in some foreign country like Australia as fuel density is now regulated by the modern pumps used at the petrol station. However the effect is very minimal for the temperature effect on petrol is only about 1% per 15F degree approximately 8.33C degree. So basically your fuel saving on cold day wouldnt be more than 2% I guess.

3. Air conditioning vs. open windows - The temperature’s soaring and you're driving on the highway. 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 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.

4. To idle, or not - 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. 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%.

5. Over-inflate your tyres - 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 - 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. However no studied done in Malaysia on this myth.

7. Put your car into 5th - 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. Higher grade of petrol, better the fuel economy - 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.