Like all drivers, you want to save gas and do what’s right for your car. But along with the tried-and-true advice, there are some well-intentioned tips that can lead you astray. Here are some common myths about fuel use and gas mileage, and the real stories behind them:
Using premium gas. When it comes to regular, midgrade, and premium gasoline, oil companies have worked overtime to drill the “good, better, best” concept into our collective driver psyche. But best really depends on the car you drive. Premium gas has a higher octane rating, usually 91 or above, and is more resistant to preignition, a condition in which fuel burns uncontrollably in the engine. Higher-performing engines are the most susceptible to that because they tend to run hotter, which is why premium is often recommended for sports and luxury vehicles. But the vast majority of cars are designed to run fine on regular: Premium won’t improve performance or fuel economy.
Using premium if “recommended.” Premium helps maximize power in engines that are designed to use it. But many can also run fine on less expensive regular gas by automatically making adjustments to the engine timing. You might not get full power when, say, accelerating or climbing hills, but most drivers will probably never notice the difference. If it says premium is required, play it safe with the right octane. If in doubt, ask your mechanic.
Letting a car warm up before driving. That was true back in the days of carburetors and chokes, but it isn’t the case with modern fuel-injected drivetrains. Engines are most efficient when they’re at regular operating temperature, and the fastest way to reach that point is to drive right after starting the car.
Choosing tires by rolling resistance. A lot of attention is being paid to a tire’s rolling resistance. The lower the rolling resistance, the better your fuel economy will be, by about 1 to 2 miles per gallon. But Consumer Reports has found that low rolling resistance can come at the expense of wet-braking performance and tread life — a poor tradeoff. It’s better to look first for a tire that provides good all-around performance in braking, handling, and hydroplaning resistance. Then use rolling resistance as a tiebreaker.
In Consumer Reports’ testing, two all-season passenger-car tires delivered excellent performance and low rolling resistance: the Continental ProContact EcoPlus+ and Michelin Energy Saver A/S.
Filling up when the air is cool. A common tip is to buy gasoline in the morning, when the air is cool, rather than in the heat of the day. The theory is that the cooler gasoline will be denser, so you will get more for your money. But most stations store the gasoline underground. So its temperature changes very little.
Avoiding no-name gas stations. Independent stations usually buy their fuel from larger, name-brand oil companies, so it’s not much different from what you’d get for a higher price down the road.
Drivers think smaller. Higher gas prices are motivating people to drive less and move to smaller and more fuel-efficient vehicles. A Consumer Reports survey found that almost three-quarters of respondents are considering buying a vehicle powered by an alternative drivetrain, such as a hybrid, flex-fuel (which can use E85 ethanol) natural-gas, or electric vehicle.
About a third of those surveyed are driving less than one year ago. And more respondents — 37 percent — consider fuel economy to be the most important factor in choosing a car. Not surprisingly, almost seven in 10 said they wanted better fuel economy in their next vehicle; 40 percent want much better gas mileage. To get it, most owners will compromise on the size or capacity of the vehicle, and about half will sacrifice comfort or amenities.
Consumer Reports writes columns, reviews, and ratings on cars, appliances, electronics, and other consumer goods. Previous stories can be found at consumerreports.org.