Car Talk's Guide to Better Fuel Economy
The softer your tires are, the greater the friction between the road and the rubber, and the harder your engine will have to work to move the car. When we check tire pressure on our customers' cars, we notice that they are often nowhere near the recommended pressure. Here's why it matters: Under-inflated tires lowers gas mileage by 0.4 percent for every one pound of drop in pressure of all four tires. So, if you're down by 10 pounds... you're losing 4 percent in fuel economy.
Don't get us wrong: This doesn't mean you should over-inflate your tires (you don't want to be riding on stale bagels), because that's not safe, either. Too much air in your tires can seriously jeopardize your car's handling. But you DO want to keep your tires right at the recommended pressure, which represents a good balance between ride, handling, and fuel efficiency.
If you're not sure what the correct tire pressure is for your vehicle, you can find it on the door to the glove compartment or on the driver's-side door pillar.
When the seasons are changing, keep an even closer eye on your tire pressure. For every drop of 10° Fahrenheit in air temperature, your tires will lose one pound of pressure.
Getting your car serviced regularly is one of the most important things you can do to maximize fuel efficiency.
Regular service can spot lots of problems that reduce gas mileage and increase pollution, such as a broken thermostat, low transmission fluid, sticky brake calipers — or even something as simple as a dirty air filter.
If you can't remember the last time you had your car serviced, take it in. In extreme situations, you might increase your mileage by up to 10 percent. So what? Well, if you drove 20,000 miles a year, you would save $250 — enough to cover the cost of the service, buy yourself a super-size falafel sandwich and still have a few bucks left over to start tipping your mechanic. (You did know you're supposed to tip your mechanic, right?)
Modern engines have such precise engine tolerances that very lightweight oil is often required, such as 0-W20 or 0-W30.
Thicker oil, such as 10W30 or 10W40, may not lubricate as well, because it won't flow as quickly into key nooks and crevices.
Thicker than required oil will also reduce your gas mileage, because it takes more energy to push through thick oil than it does through thinner oil. Check your owner's manual for the recommended viscosity, and ask for it specifically when you get your oil changed. You don't just want whatever they have on special this week.
Use the grade of gas you need and nothing higher.
Does your owner's manual say "Premium Unleaded Only"? No? Then don't ever use premium fuel. There. We just saved you 40 cents a gallon... or $8 on a 20-gallon fill up. If your engine is designed to run on regular gas, there's absolutely no benefit to putting in "high test." It pollutes more, it costs more, and doesn't give you any benefit in performance or fuel system cleanliness.
Now, what if your car DOES call for minimum 91 octane? Well, next time you buy a car, dumkoff, check what kind of fuel it requires first. We've always said that once you buy the car, you're stuck. You've got to use 91, because your high compression engine will ping if you don't. But now, most cars have "knock sensors," that retard the timing via the engine management computer (effectively lowering the compression) to protect the engine, in the event that you happen to get some bad gas, or have an emergency and can only get regular grade fuel. So we got to thinking, what would be wrong with using the knock sensor all the time? What if you put regular gas in the car all the time and let the knock sensor do its job and retard the timing? You'd have a little less power, but that extra 8 bucks a fill up might be more important to you than power right now. It would be to us.
It's a controversial theory, we admit it. But that's never bothered us before. And we can't think of any long-term effects of driving with the knock sensor retarding the timing. So our position (for the time being) is... use regular. Who cares? Now, if there are any actual automotive engineers in the audience who have worked on knock sensors, who want to tell us why we have our heads up our keisters, feel free to write to us. And if we're convinced that we're wrong, we'll happily change our recommendation.
Wind resistance increases dramatically with speed. That's why aerodynamics have become so important in the last 15 years, and why all of our cars now look like jelly beans.
How much does it matter? Consider this: for every ten miles per hour you floor it, you lose as much as 15% in fuel economy. What's that mean for your retirement account? For every 1,000 miles you drive, figuring gas at $2.50 a gallon and 25 MPG fuel efficiency, you'd save as much as $15 if you drove 10 mph slower. Over the course of the year, that's enough to buy that nuclear powered, stainless steel cappuccino machine you've been coveting — and have enough left over for beans, too.
Our advice? Slow down. You'll be a safer, more relaxed driver, and you'll increase your fuel efficiency. And, believe it or not, due to an unexplained Einsteinian time warp, you'll also get to your destination in about the same time.
Getting into the highest gear you can, at the lowest possible speed, will save you plenty of gas.
Why? Because you use less gas when the engine is turning slowly. The slower the engine turns, the fewer the number of explosions in the cylinders. And fewer explosions means less gas consumed.
So, if you drive a manual transmission car, shift sooner. As long as the engine doesn't buck, shudder, or ping, you're fine. You'll sacrifice the ability to accelerate quickly — but you can always downshift if you need to accelerate.
Why is it that everyone feels they have to accelerate going up a hill?
It turns out that accelerating uphill is a fabulous way to burn up enormous amounts of gas. Don't believe us? If your car has a display that shows your instantaneous gas mileage, try it out. You'll see your mileage plummet — from 25 or 30 MPG... down to 6 MPG — or sometimes even as low as 2 or 3 MPG.
So, don't try to increase your speed when you're climbing a hill — just maintain the same speed, or even allow the car to go a little slower. Heck, it's a hill! Your wallet will thank you.
Every time you step on your car's brakes, you're wasting gas.
Why is that? Simple. Every time you use the brakes, you're wasting the "acceleration" you've already used. Instead of moving your car, that energy is being transformed into steaming hot brake pads.
How do you use the brakes less? Anticipate. If you're at a stoplight, don't speed away when there's a good chance you'll have to stop again soon. Accelerate slowly, and then coast to the next light. If you see a need to stop up ahead, coast. Don't continue to accelerate and then brake at the last minute. If you anticipate your stops, you'll cut down on your wasteful acceleration, and save lots of fuel.
You know that Thule roof rack you keep on your car to convince people that you're really outdoorsy? (Even though you drive a Volvo.) It's costing up to 5 percent in MPG. So unless you need the rack to boost your flagging self-esteem, we suggest you pull off the entire rack. That also goes for standard luggage racks, kayak holders, ski racks, Labrador retriever holders and all the cross bars that go with them. Put it in the garage, and toss the rack back on the roof when you really need it. You'll reduce your aerodynamic drag significantly.
What's your MPG when you're idling? It's negative! You're actually burning gas... and going nowhere.
If you're sitting outside a tattoo parlor waiting for your grandmother, and you know it's going to take her a good 15 minutes to get that new Komodo dragon tattooed on her left butt cheek, turn off your engine. You're just burning money. Some people have heard a myth that it takes more gas to start a car than to run it. So they use that as an excuse to leave a car idling. It's complete B.S. If you're stationary for more than a couple of minutes, shut it off, and save gas.
This tip also applies to warming up the car. Unless it's below freezing, cars don't need to be warmed up at all. Driving them gently is the best warm up there is. If it's 25 degrees out, you might want to let it warm up for 30 seconds. If it's 10 degrees out, warm it up for a minute. If it's -10 degrees out, move somewhere warmer.
Some members of our extended family seem to enjoy driving around with, say, 200 pounds of "dead" weight in the back of their cars. And, as it turns out, each 100 pounds in the trunk will reduce your fuel economy by 1 to 2 percent.
So, take a moment, rifle through your trunk, and dispose of any extra bowling balls that are rolling around back there.
If you don't need to run your air conditioner, don't. Your car's air conditioner forces the engine to work harder — and that's energy that could instead be used to move your car forward. So if it's 74° Fahrenheit outside, open the windows instead of wasting fuel running the AC at 72° Fahrenheit.
Here's a tip e mailed to us from our pal Bernie Gwalthney:
I saw the following letter to the editor in the St. Petersburg (Florida) Times on October 9, 2005: In an effort to cut down on unnecessary driving, I've decided to stop and ask for directions when I'm lost.
Richard Parvin, Clearwater
Now, just imagine if every guy stopped and asked for directions when he got lost. The US would never import another barrel of oil! (Okay, we're kidding. But, you have to admit it: the guy's got a good point.)
Source: Car Talk