Gasoline plays a big role in daily life for many of us, fueling our journeys and draining our wallets. And over the years, many myths have developed about gas and how to spend less on it.
Here we set the record straight, separating what’s true and what’s false among commonly held perceptions about gas…
False. There is a minimal amount of sediment in the bottom of most gas tanks. Also, the fuel pump in your tank has a filter screen, as do the valves leading into your engine, to catch any debris.
False. It’s a waste of money because some of the additional gas you’re forcing into your tank may be drawn into the nozzle’s vapor recovery system and rerouted back into the station’s storage tanks instead of your car. Moreover, if the fuel level in your car gets too high, it can spill into the vapor hoses at the top of your tank and leak into the evaporative emission control system. That won’t do permanent damage, but it will cause your engine to temporarily falter and run poorly when you are driving, and it could trigger your “Check Engine” light.
True. What distinguishes the two dozen pricier “top-tier” brands, which include BP, Chevron, Conoco, Costco, Exxon, Mobil, Phillips 66, Shell, Texaco and others, is higher levels of detergent additives in both regular and premium gas. These additives help reduce carbon deposits that build up on your engine’s fuel injectors, intake valves and combustion chambers. If you use generic gasoline, it’s a good idea to fill your tank with a brand-name gas a few times each year, especially in older cars. You could see reduced emissions and a slight improvement in power and performance—but don’t expect to get better gas mileage. Whether they have a big brand name or not, all gas stations in the US are governed by stringent regulations regarding the quality, storage and pumping of fuel, and stations typically get their gas from the same or similar refineries.
True. Running low-octane fuel regularly in an engine built for premium can result in sluggish performance, lower fuel economy and, in worst-case scenarios, physically damage the engine. The knocking caused by low-octane gas puts pressure on the pistons and valves.
Generally false. You typically get no better performance, gas mileage, longevity or other benefits from premium gas unless your car requires it. “Premium” is a marketing term that simply indicates that the gas has a higher octane level, meaning that it takes more compression inside the engine to ignite it. Certain luxury and sports cars have powerful, high-performance engines that need premium-grade gas (91 or 93 octane) because regular gas (87 octane) tends to ignite too quickly for their engines. That creates an improper fuel-air mixture that disrupts the proper working of the engine and causes a knocking or pinging sound.
Exception: Older (model year 1995 and earlier), heavier cars made for regular gas may experience knocking under severe engine strain such as towing big loads up mountain passes. Using premium gas may stop the knocking and improve engine performance.
False. The Environmental Protection Agency has tested hundreds of these products over the years specifically for their better mileage claims. It has not found any that make a significant difference.
True. Since 2007, Congress has required oil companies to blend ethanol, an alcohol distilled from corn, into gasoline. Most fuel sold in the US is “E10,” meaning that it may contain as much as 10% ethanol. Vehicles typically get three to four fewer miles per gallon on E10 than on straight gasoline. Gas stations do not reveal the exact amount of ethanol in their E10 blends, but some actually use far less than 10% ethanol. This is the reason you may get better mileage using fuel from one station than from another.
