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February 10, 2017

5 Common Refueling Myths Debunked

Refueling your car is an often misunderstood act and it can be quite confusing to uninitiated car owners. Most won’t even care what goes on after the nozzle goes into the tank for as long as the fuel needle reads “full” after a couple of minutes. This carefree attitude towards pumping gas has led to the spread of refueling myths, some of which have spread again and again.

But with refueling becoming a weekly routine for everyone, now is a good time to get educated and break that cycle of ignorance. It’s time to set the record straight and debunk these 5 popular refueling myths.

Myth #1: The higher the octane, the better. 

Go to any gasoline station and chances are, you’ll come across a number emblazoned on the pump. These numbers, ranging from 91-100 signify the RON or Research Octane Number of the fuel you’re loading up on. In the simplest sense, RON determines the fuel’s anti-knocking quality or its resistance to detonation.

With modern cars running ever-complex computer systems that control combustion timing, cars can adjust for a variety of fuel grades without any detriment to fuel economy or performance. Thus, you’re not going to do any good by simply filling up on fuel with the highest octane available. Simply stick to the manufacturer’s recommended octane which is either stickered on the inside of your fuel cap or indicated in the owner’s manual.

When it comes to diesels, things can get trickier. For one, there’s no number figure stickered on the pump. That said, diesels still do need to adhere to a standard and in this case, it’s the Cetane Number. Cetane rates how short the ignition delay is (time interval between start of injection and combustion); so in effect, the higher the Cetane Number is, the shorter the delay. In order to meet Euro IV, the Philippine government mandates a minimum Cetane Number of 50. For premium diesels, this number can go up to 55.

Unlike its gasoline counterpart, fuel companies don’t advertise that using premium diesel gets you more power or better efficiency; simply because they don’t. What you do get is a combustion that produces less soot. Together with more fuel detergents and other additives, using premium diesels can produce cleaner tailpipe emissions and smoother idling. Using premium diesels may be more helpful for vehicles equipped with exhaust treatment systems.

Myth #2: It’s best to fill up when it’s cold because you get more fuel. 

This myth isn’t something new. The reasoning behind it is when the fuel is cooler, it’s denser and denser fuel will pack more energy in the same amount of space. Thus, you’ll get more “bang” for your buck. But while density may change with temperature, the fuel pumped by gasoline stations is stored in underground storage tanks well below the surface. This means the stored fuel is almost always at a constant temperature.

One of the only times that you’ll find warmer, less-dense gas is if the fuel doesn’t have the time to cool off after being pumped into the underground tanks during delivery. Yet, the nature of gasoline means its temperature stabilizes quickly resulting in a volume difference of less than 1 percent—enough to be negligible at the pump.

Myth #3: It’s okay to top off your gas tank after the nozzle automatically shuts off. 

This is something everyone’s been guilty of at least once. After the nozzle automatically shuts off, you top off the gas with a few extra pumps until you reach the tank brim.

Those few extra pumps after the nozzle automatically shuts off aren’t worth the trouble. It can actually harm your car’s evaporative control system, mainly the evaporation canister that prevents fuel vapors from escaping into the atmosphere. This system is designed to re-burn vapors, not liquid gasoline that gets pushed out of the gas tank when you fill up. Topping off fuel is the number one cause of the canister’s failure and can be costly to repair.

Myth #4: Using cellphones when refueling will cause an explosion.

While it’s true that gasoline stations post stickers on pumps warning motorists to turn off or not use cellphones while refueling, there’s actually no documented case where a mobile phone caused a gas station fire or explosion.

The most likely reason mobile phone usage is discouraged while refueling is that it can cause distractions. When dealing with a volatile and flammable chemical, it’s best to pay attention to what’s going on. That Facebook update or Snap Chat video can certainly wait an extra few minutes.

Fires are more commonly caused by vehicles left running while refueling. So it’s best practice to shut your engine off and if you’re riding a motorcycle, get down before the start of any refueling.

Myth #5: Using no-name brands is bad for your car.

While it’s true that top-tier brands have proprietary additives that help clean the engine, using fuel from a smaller, independent player isn’t detrimental to your car. This is because fuel from independent brands still has to meet legal requirements to be sold to the public. In fact, it’s not entirely surprising to have smaller players supplied by a major oil company, but simply not have fuel sold under their name.

What’s more important is to pay attention to the quality and condition of the gas station itself. If the looks decrepit imagine what condition those underground storage tanks could be in. If you own a private vehicle, avoid refueling in areas where there’s a large population of public utility vehicles like jeepneys. This price sensitive situation can become an avenue where gas stations would resort to various short cuts just to increase profits such as selling tainted gas. It’s no assurance, but larger gas companies do have better quality assurance measures and it can prevent this sort of incidents.


  1. I agree with all of these except the last one. The problem with no-name fuels is that you can't be sure with the quality of the additives it puts in the gas, whether it uses methanol (very bad!), if the pump is properly calibrated, and how often the government regulatory agency has tested the no-name brand's fuels. It's one thing to say that there are laws and regulations on the sale of fuel, it's quite another to say that off-brand X is following the law scrupulously.

    The gas may be supplied by Petron or Shell, but it usually does not include the proprietary additives that they add to the gas. And these additives makes all the difference between a clean burning fuel, and something that leaves too many residues to the engine.

  2. The last part is more like "dont refuel on those bottled fuel on the side of the road"
    Some mix it with cheap or stolen diesel from company trucks to maximize profit.

  3. Does myth #1 apply to diesels? I don't think there's a manufacturing spec for diesels to get the regular or premium kind. Does pumping the premium diesel give anything to give worth to the 2.50 increase per liter?

    Thanks for an answer

    1. Updated the article to reflect premium diesels as well.

    2. Thanks! Always wondered what the difference was between regular and premium

  4. I disagree with Myth #4 please do research again. I worked for an Oil and Gas design company. There are actual videos that showed how cellphone triggered an explosion in a gasoline station. Petrochemical Plants won't put those sticker without a fact.

    1. Cellphone use per se won't trigger an explosion or fire.

      Static electricity can.

      You can read about it.

    2. there is an electric static everywhere, not only triggered when using cellphone.

    3. I actually checked and the chances of triggering an explosion or fire via static electricity is also very low. It seems gasoline station fires are caused more by a running engine (see above).

    4. go and see mythbusters, static can cause fire note cellphone/smartphone..

  5. Its the combination of "fume" which is highly combustible....triggerd by anything static...not only cellphone....its the probability of the two together that is what they want to avoid...consequences are high...better be safe than "kaboom"...


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