We're not sure where some of these car myths started. Things like mixing low- and high-octane gas to get an octane level higher than high—that had to be a contest between Dumb and Dumber. The campfire-story genesis doesn't seem appropriate either, because some myths are actually based in fact, maybe old facts, but facts nonetheless. We'll start with that old grudge move: Sugar in the gas tank.
Not So Sweet.
Sugar in the gas tank will blow it up. The jerk who thought this one up assumed the sugar would melt, ooze into every nook and cranny of the engine and solidify once the engine was turned off and cooled down. Think giant candy mold. Wrong.
Back in 1994, researchers at Berkeley figured out sugar doesn't dissolve in gasoline. Oops. Sugar in the gas tank can play havoc with your fuel filter or require the gas tank be pulled and cleaned, but destroy the engine. Nope.
Coming Out of the Closet?
Mothballs increase octane. Believe it or not, this was once true. During World War II, naphthalene was the active ingredient in mothballs and octane ratings of gasoline were 60 to 80. Since naphthalene's blending motor octane number is 90, mothballs could increase the fuel's octane rating.
Today, though, modern mothballs contain para-dichlorobenzene (try saying that five times fast!) rather than naphthalene, but the latter is making a comeback due to toxicity concerns of the former. But considering the higher octane levels of today's gasoline and the fact that naphthalene has a high melting point and can block jets and filters, mothballs are best kept in the closet.
What Kind of Fuel Am I?
Does mixing low- and high-octane gasoline result in higher octane than the high octane alone? If you want to test this yourself, be sure you add one when the gas tank is half full of the other. Trying to fuel up with half of each in an empty tank could result in a pocket of pure low or pure high fuel surging through the system. The two fuels have different density levels and may not mix immediately.
Don't bother, however, because you won't get a higher octane even with a well-mixed blend. It's simple math: half a tank of 87 plus half of 91 equals 89 octane. Mixing leaded high and unleaded high is equally useless.
Storing a battery on the ground or on concrete will discharge it prematurely. Like the mothball myth, this was once true. At one time battery cases were made from natural rubber and would discharge more quickly depending on where they were stored.
Today the cases are made of polypropylene or other modern materials that allow them to be stored anywhere with no difference in the normal rate of discharge. Of course, if you leave a battery stored long enough anywhere - even in the car - it will discharge.
Keeping You in Suspense.
Driving fast on a washboard road smoothes out the drive. Finally, a true one. Maybe not a wise idea since you'd be hydroplaning on the edge of control, but at least the ride is smoother than creeping over the bumps. Just watch coverage of the Baja 1000, and you'll see what we mean.
At higher speeds, the wheels skim the surface of the ruts. As you slow down, the wheels feel every ripple. A team of myth freaks tested this one out, even fabricating a steel model of the legendary washboards in Australia. They used water in glasses, a suspension gauge and cameras focused on wheel action. The simulated rut test proved that a washboard road smoothes out at 70 mph. But don't try that at home.
Driving with the tailgate down will improve gas mileage. Debunked. In fact the exact opposite is true. With the tailgate in place, a bubble of stagnant air forms in the bed of the truck creating the same kind of aerodynamics that a tonneau cover does. With the tailgate down, that bubble doesn't form, wind resistance increases and gas mileage decreases.
And will literal tailgating increase gas mileage? No, but it could get you a ticket. The theory is based on the practice of drafting during auto races. You tuck in just inches behind another fast-moving vehicle and ride on its coattails, letting the leader burn up fuel by parting the atmosphere. You may have tried this behind a semi on the highway. Think about it: a stock car hitting 200+ mph and a semi at around 65 mph. The theory doesn't hold up. If you don't get a ticket, you'll probably end up with dings in your front end from the rocks the big rigs kick up.
A really loud stereo can shatter your windshield. The same team that tested the washboard theory proved this one true—sort of. The scene of the test was the 'dB Drag Racing" car speaker competition at Spring Break Nationals in Florida. The vehicle was an old Mercedes gutted to make room for 51-inch subwoofers (normal is 10 inches). The speaker system was powered by the engine (normal systems are powered by electromagnets). A crankshaft/push rod system literally drove the speakers to 161.3 dB inside the car (a jet engine with 16,000 lbs. of thrust hits 165 dB, and you'll temporarily damage your hearing at 140 dB). Unfortunately, the pressure blew the sunroof off the car before the windshield cracked. But, in theory, a monster system like the one used in the test could blow out the windshield, if you secure your sunroof first.
Running gasoline in a diesel engine will blow it up. Not. The diesel engine simply won't run long enough on gasoline to blow up. Gas engines require a spark to ignite the air/fuel mix. Diesels ignite when the fuel is introduced into the cylinder with highly compressed air. If you put gasoline in a diesel engine, it vaporizes and ignites prematurely causing the engine to sputter, knock and stall out. But not explode.
Aspirins in a battery's cells can rejuvenate it. True! The acetylsalicyclic acid in the aspirin combines with the sulfuric acid in the battery, in some cases, allowing for one more charge depending on the level of battery deadness. Recommended dosage: two aspirins in each cell then wait an hour before you try to start the engine and call me in the morning. The combination of acids forms acetic acid, which has the potential to shorten the battery's life. But given the choice of being stranded or dropping a couple aspirin, the damage is not significant. Got any more automotive myths to debunk or confirm? Send us an email, and we just might follow up. But only if they sound reasonable—or totally crazy.