Fuel Myths Quiz

Biodiesel is an alternative or additive to diesel fuel that can be used in diesel engines with little to no modifications to the engines themselves. It's not made from petroleum -- instead it comes from plant oils or animal fats that have been chemically altered.

In fact, Rudolf Diesel, who patented the diesel engine in 1892, had originally considered vegetable seed oil as fuel for his invention.

Because they are harder and roll more easily, properly inflated tires burn less fuel than underinflated tires.

An estimated four of 10 vehicles on the road have at least one underinflated tire. Pressure that is 3 pounds per square inch (psi) below the recommended reading may reduce gas mileage by 1.5 percent or more. Actually, the Environmental Protection Agency warns that running tires at 20 psi or lower can easily cost you a full mile per gallon!

So find out your car's recommended tire pressure (typically on a sticker inside the glove box door or on one of the doorposts), and check it every 30 days to make sure it's right on the money.

Don't believe everything you see in the movies. Cars practically spontaneously combust on the big screen, but in real life it takes a very specific set of circumstances for a car to turn into a ball of flames.

In order for a car's fuel tank to catch fire, it would have to rupture in such a way that the gas sprays out in a fine mist at a concentration of 0.8 to 6 percent gasoline vapor in the air and come into contact with an ignition source. Since gas tanks are pretty well protected, and the ignition is at the other end of the car, this is pretty darn unlikely.

To further contradict the world of movie physics, bullets do not spark, so while a bullet can make an unsightly hole in the side of the car and an annoying leak in the fuel tank, it will not cause the vehicle to instantly explode.

Revenge is sweet, they say. And what better way to exact sweet revenge than to ruin someone's car with a bag of sugar? If you empty the bag into the gas tank, the sugar will make its way into the engine, caramelize from the heat, and then harden like rock candy once the car cools down, effectively destroying the engine ... right?

Wrong.

Sugar does not dissolve in gasoline, and filters prevent any solids in the fuel from getting into the engine, so it is likely to remain intact in the gas tank. The only harm you can hope to inflict by putting sugar in someone's gas tank is the inconvenience of a trip to the mechanic to replace the fuel filters and clean out the tank.

Aerodynamic studies show a pickup truck is most fuel efficient with its tailgate up. It seems the upright tailgate causes air flowing over the roof of the cab to collect as a stagnant "dome" in the cargo bed. As speed builds, this dome, which tapers in a teardrop shape near the tailgate, acts as an aerodynamic ramp that forces airflow over the tailgate, to the benefit of fuel efficiency.

Disrupt this flow by dropping or removing the tailgate, and air coming over the cab is left to swirl around in the cargo bed, degrading the truck's aerodynamics and hurting fuel economy.

While there are many warnings circulating on the Internet -- and even posted at gas stations -- about the hazards of using a cell phone while pumping fuel, there are no documented cases of a cell phone ever causing a fire or an explosion at a gas station. Nor has anyone scientifically demonstrated that such a thing is even possible.

While some fuel station fires were initially attributed to cell phone use in the press, further investigation has always turned up another cause.

A higher octane rating does not necessarily equate to better performance. The owner's manual will tell you what type of gasoline is recommended for your car, and most cars are designed to run on regular gasoline. Unless you drive a high-performance car that requires a higher-octane gasoline to prevent engine knocking, the only real difference you'll notice from upgrading to a high-octane premium gas is how much more money you are spending at the pump.

Diesel fuel has a higher energy density than gasoline. On average, 1 gallon (3.8 L) of diesel fuel contains approximately 155x106 joules (147,000 BTU), while 1 gallon of gasoline contains 132x106 joules (125,000 BTU). This, combined with the improved efficiency of diesel engines, explains why diesel engines get better mileage than equivalent gasoline engines.