6 gas-saving myths

[Wt_know]

Sure you want to save gas, but there's a lot of bad advice on how to do it. Some of it makes no difference, and some of it can wind up costing you.

By Peter Valdes-Dapena, CNNMoney.com staff writer

Last Updated: May 15, 2008: 3:59 PM EDT

NEW YORK (CNNMoney.com) -- With gasoline prices hitting record levels, it seems everyone has a tip on how to save fuel. Much of the advice is well-intentioned, but in the end, much of it won't lower your gas bill.

 

Here's a look at a few misconceptions:

 

#1. Fill your tank in the morning

You may have heard that it's best to fill your gas tank in the early morning while the fuel is cold. The theory goes that fluids are more dense at lower temperatures, so a gallon of cold gas actually has more gas molecules than a gallon of warmer gas.

 

But the temperature of the gasoline as it comes out of the nozzle varies little during the course of the day, according to Consumer Reports, so there's little, if any, benefit, to getting up early to pump gas.

 

#2. Change your air filter

Maintaining your car is important, but a clean air filter isn't going to save you any gas. Modern engines have computer sensors that automatically adjust the fuel-air mixture as an increasingly clogged air filter chokes off the engine's air supply.

 

While engine power will decrease slightly as the air filter becomes clogged, a lack of performance or an increase in fuel consumption will be negligible, Consumer Reports says.

 

#3. Use premium fuel

With prices already over $4.00 a gallon, premium gasoline is a hard sell these days. But a lot of drivers think because their owners' manual recommends premium, they'll get better fuel economy with it. Really, they may be paying more money for nothing.

 

Newer cars for which premium is "recommended" - but not "required" - won't suffer with regular fuel. Modern engine technology comes to the rescue again. When sensors detect regular instead of premium fuel, the system automatically adjusts spark plug timing. The result is a slight reduction in peak horsepower - really, you'll never notice - but little or no reduction in fuel economy.

 

Always check your owner's manual before putting anything into your car. And if your car runs badly on regular, by all means, go back to the pricey stuff. (See editor's note at bottom)

 

#4. Pump up your tires

Proper tire inflation is important for a number of reasons. Under-inflated tires are bad for handling and can even cause a crash. Improper tire inflation also causes tires to wear out faster and to heat up more, which could trigger a dangerous high-speed blow-out.

 

According to on-the-road driving tests by both Consumer Reports and auto information site Edmunds.com, underinflated tires reduce fuel economy, so proper inflation is key.

 

But you should never over-inflate your tires. They'll get you slightly better fuel economy because there will be less tread touching the road, reducing friction. But that means less grip for braking and turning. The added risk of a crash isn't worth the extra mile a gallon you might gain.

 

#5. To A/C or not A/C

There's no question air-conditioning makes extra work for the engine, increasing fuel use. But car air conditioners are much more efficient today than they used to be. In around-town driving, using the A/C will drop fuel economy by about a mile a gallon.

 

Meanwhile, driving at higher speeds with the windows down greatly increases aerodynamic drag. As speed increases, drag becomes more of an issue, making A/C use the more efficient choice at high speeds.

 

At most speeds and in most vehicles, A/C use drains slightly more fuel than driving with the windows down, contends David Champion, head of auto testing for Consumer Reports. "My final take on is that it's very close," says Phil Reed, consumer advice editor for Edmunds.com. "It's hard to measure the difference and every vehicle is different."

 

The best choice - if temperature and humidity allow - is to keep the windows rolled up and to turn the A/C compressor off. You can keep the fans running to blow in air from the outside, but your car will be as aerodynamic as possible while still letting you breathe. You will save gas, but the fuel economy improvement will be slight.

 

#6. Bolt-ons and pour-ins

Before you buy a device that's supposed to make your car more fuel-efficient or pour in an allegedly gas-saving additive, ask yourself this: Don't you think oil and car companies aren't doing everything they can to beat their competitors?

 

If BP (BP) could add something to its gasoline that made cars go farther on a gallon, cars would be lining up at the company's pumps. Sure, people would burn their fuel-saving BP gas more slowly, but then they'd drive right past rivals' gas stations to come back to BP for more. BP stations could even charge more for their gas and still sell tons of the stuff.

 

So if there really was an additive that made gas burn up more slowly, it wouldn't be sold over the Internet one bottle at a time.

 

Likewise, car companies are already spending big bucks to increase fuel mileage. If General Motors could make its cars go significantly farther on a gallon simply by putting a device into the fuel line, don't think for a second it wouldn't be doing that. GM's car sales would go through the roof.

 

"There are a number of these gas-saving devices that are generally useless," says Champion.

 

But drivers who try them will swear they work. In reality, it's probably an automotive placebo effect, says Reed. Buy one of these devices or additives, and you're like to pay extreme attention to your fuel economy and how you drive.

 

Of course it can't hurt to keep a close eye on your driving habits -- and what kind of car you drive. In the end, that can make the most difference in saving gas.

 

Gas prices have climbed to record levels. Are you feeling the pinch? Tell us how gas prices are affecting you and what you're doing to cope. Send us your photos and videos, or email us to share your story.

 

-Editors note: This story was revised from an earlier version to clarify that the advice to use regular gas instead of premium may not apply to all cars.

 

First Published: May 13, 2008: 11:38 AM EDT

Edited May 17, 2008 by Wt_know

[Genie47]

Tell that to SG drivers. Speeding here and there. Speeding uses more fuel! Don't people know this?

 

Taxi driver lagi better. In fact they should be more worried about fuel economy since it eats into their takings. Speed here, speed there. Worse. IDLE and khoon in taxi with A/C on. Passenger pay $20 pay $10 for diesel. Somehow I think they are poor at running their own business.

[Albeniz]

Point 3: Premium Fuel myth

 

I used to pump Esso/SPC-92/95 and had been constantly getting 9.5km/L or even worst.

Recently there was a discount on Shell Vpower. With that tank, I got 11.2km/L.

I am still trying to confirm if this is a "myth" by trying out a few more tanks.

 

What's in Vpower which might had caused that improvement?

[Showtime]

point #1 is not a myth. At the pump, you pay by the volume. When it is colder, you get more mass for each unit volume. And what the ecu computes is a mass air fuel ratio, not a volume air fuel ratio.

 

take airliners, which travels from hot singapore to cold montreal for example. for a given volume of fuel, the actual amount of fuel by mass is going to be very different. And in cruise at 41,000 ft for eg, where the outside air temp is -56 deg celsius, the mass of fuel is gonna change drastically.

 

Therefore airplanes take in fuel by mass, not by volume for the above reason. The same thing can apply to cars, with very much less effect, but still measurable. 25 degrees on a cold night, vs 35 degrees on a hot day. Think about it.

 

of course if the report is really true that the difference of fuel temp is negligible, the gains might not be worth the trouble.

 

The question would be are the underground tanks heat insulated?

Edited May 17, 2008 by Showtime

[Wt_know]

"There are a number of these gas-saving devices that are generally useless," says Champion.

 

this one chopped and signed ... very few will disagree

[Davidklt]

Even if its true.

 

the savings would be neligible.

[Route88]

Taxis like to blow carbon. Even the white hair ones

[Drive_carcar]

I wonder why there's no mention about coasting i.e. putting gear in the neutral when the car has gathered enough momentum. I had a friend who swears by that. He would let the car gain enough momentum, and then depress the clutch to shift to neutral.

 

Then there's another who says that engine braking actually waste more fuel apart from wearing out the clutch faster.

 

And finally, my own pet theory..... I think installing spoilers probably increases drag and decreases fuel economy.

[Genie47]

Confirmed a myth lah! The moment you pump premium petrol, you tend to be conscious of your fuel saving effort and keep your speed. Why? You revv hard, premium petrol burn faster, money burn faster! You will feel the pinch harder!

[Accentrix]

Point 3: Premium Fuel myth

 

I used to pump Esso/SPC-92/95 and had been constantly getting 9.5km/L or even worst.

Recently there was a discount on Shell Vpower. With that tank, I got 11.2km/L.

I am still trying to confirm if this is a "myth" by trying out a few more tanks.

 

What's in Vpower which might had caused that improvement?

 

I have the same experience when using Vpower. Anyone figured it out yet why using Vpower makes a difference? BUT I have to say that it's too EX for me to keep pumping Vpower all the time despite the apparent difference it makes.

[RadX]

However, should you calculate the price per km, does using V-power make it cheaper? If so, you shld consider changing it.

When I pumped V-power, I got $0.17 per km. When 95, was $0.19 per km. 2c does not justify changing liao

[Zakuii]

i'll advice you to try longer. I've used vpower few years ago when it is still very much affordable. no diff with other 92/95/98 petrols.

[Shemmy]

Point 3: Premium Fuel myth

 

I used to pump Esso/SPC-92/95 and had been constantly getting 9.5km/L or even worst.

Recently there was a discount on Shell Vpower. With that tank, I got 11.2km/L.

I am still trying to confirm if this is a "myth" by trying out a few more tanks.

 

What's in Vpower which might had caused that improvement?

 

I don't know what causes the improvement but i really do get better mileage with Vpower. In addition, better performance.

[Shull]

Speeding uses more fuel! Don't people know this?

 

those that you see are running on pak lah's petrol.. me included..

[Zakuii]

If you are driving a sports car like WRX, you may get better power off premium fuel. Not sure about FC though...

 

See the video below.

 

http://youtube.com/watch?v=0QGCYLwTCGI

http://www.youtube.com/watch?v=iKQm8buu8dk

Edited May 17, 2008 by Zakuii

[Albeniz]

Confirmed a myth lah! The moment you pump premium petrol, you tend to be conscious of your fuel saving effort and keep your speed. Why? You revv hard, premium petrol burn faster, money burn faster! You will feel the pinch harder!

 

Not true. I drive like a 70 year old Ah pek with both types of fuel.

No special treatment from me.

[Kklee]

Point 3: Premium Fuel myth

 

I used to pump Esso/SPC-92/95 and had been constantly getting 9.5km/L or even worst.

Recently there was a discount on Shell Vpower. With that tank, I got 11.2km/L.

I am still trying to confirm if this is a "myth" by trying out a few more tanks.

 

What's in Vpower which might had caused that improvement?

 

I have the same experience when using Vpower. Anyone figured it out yet why using Vpower makes a difference? BUT I have to say that it's too EX for me to keep pumping Vpower all the time despite the apparent difference it makes.

 

Is your ride heavy or >50% loaded everytime?

 

V-Power is RON98. On mine, any RON98 gives slightly more power. Perhaps since more power, one has to step and hold on the accelerator less. Also between Mobil 5000 vs Shell 95, Shell gives better mileage.

[Boyboy]

based on my experiece thus far with the few rides that i've driven on regular basis.

 

kangoo, old camry, new camry, getz...

 

tyres shd be overinflated by 5-10% for optimal wear. default pressure usually results in greater shoulder wear as compared to center thread wear.

 

experiment to find ur optimal pressure. my take is that the rating errs on the side of comfort. of course, dun overinflate by 20% just to save on petrol and skid because of low grip, or wear out the tyre center portion in no time

 

also, tailgating is one of the best ways to waste fuel, especially so with AT vehicles. everytime see pple smell backside then brake, then smell backside again. i just laugh at those idiots

 

of course if u really in a rush and need to intimidate pple, i got no comments. but for those who make this a regular habit in moderate traffic

 

then again, maybe most pple are really in a rush. stressful life?