Are these fuel economy myths, really myths?
Are these fuel economy myths, really myths?
I cut & pasted this from Yahoo’s main page; are these tips bogus?
#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 if they stick with it. Really, they’re paying more money for nothing.
Even cars for which premium is recommended 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 no reduction in fuel economy.
#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 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.
So many BA’s I hate doing the vote thing, it comes off as being indecisive, oh well.
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Filed under Gas Conservation FAQ by on Feb 20th, 2011. Comment. 
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Comments on Are these fuel economy myths, really myths?
Sounds to me like they make a good argument, thanks for the info.
Gee!…Thanks for all that.
All of them are generally not going to work.
1. Gas tanks are usually underground. Stick something underground, and its temperature will remain virtually constant from day to day, and sometimes from season to season.
2. This is correct. Not only that, if you don’t compensate for reduced power by putting your foot to the floor, a clogged filter COULD actually improve your fuel economy. (Unlikely, and not by much)
If you’re driving an old carbureted car (so 1980s or earlier), or a really bad fuel injected one, it might not adjust the fuel delivery to compensate for decreased air flow. In that case you could end up putting a lot of fuel into the car that will end up not being burned because there isn’t enough air (running rich). That does waste fuel. But modern fuel injection, when it works properly, is supposed to prevent that.
3. If your car is designed for premium (it will say in the owner’s manual, and possibly on the filler cap) use premium. Using lower grades will lead to degraded performance and MAY lead to degraded fuel economy.
Also, if you have detonation (“knock”) in a non-premium fueled car, running premium can help you there.
Otherwise, if the owner’s manual says use 87 octane, run 87 octane.
4. Correct. It can help your fuel economy, but will hurt everything else.
5. Correct. It is hard to say for all cars. One thing you can say is that AC makes a bigger difference with smaller engines. (So the “windows vs AC” transition speed should be higher on a Metro than on a Mustang)
6. Correct. The vast majority of doodads and chemicals that people claim will give you improved fuel economy, won’t. They are snake oil pure and simple.
EXCEPTIONS: “chips,” ECU reflashes, replacement ECUs for some cars that have either conservatively or just BADLY programmed computers. Cars that are famous for benefitting from such upgrades include: Volkswagen diesels, some other VWs; Subarus; many diesel pickups.
Also, if a car has a poorly designed intake or exhaust system, replacing it with something that allows air to flow more freely can help performance, and sometimes fuel economy.
Underdrive pulleys. These are smaller, lighter (meaning less mass to speed up and slow down, thus less energy used) pulleys for things like the AC compressor and alternator. They reduce the load these devices put on the engine, but also reduce their performance. It’s a trade-off.
Lighter parts: less mass = less fuel. Not worth the price for fuel savings alone.
“Final drive” gears. The gear ratio in the differential. If it is a higher ratio, it means the engine turns less for every turn of the wheels. This can (and usually does) save fuel, but at the cost of acceleration.
#1 – Myth.
#2 – Keep your air filter clean! A clean air filter can drastically IMPROVE fuel economy. On my last car I had a K&N filter (washable & reuseable) and when as it got dirtier, my mileage would degrade. When I got really lazy about cleaning it, I could lose anywhere between 100-150 kms (60-95 miles) per tank. Once it was cleaned, I would get all that back again.
#3 – Myth. Only use premium if a) recommended by the manufacturer, or b) your engine is having pre-ignition or knocking.
#4 – True – filling your tires to the max recommend psi will help your lmileage by reducing rolling resistance (something harder will roll easier than something softer). This will NOT reduce the contact patch between the tire and the road!
#5 – A/C takes alot of power to run. Stick to the just the vents and the fan as much as possible, unless it’s just too hot.
#6 – Myth – as per reasons you mentioned.
But keep your air filters clean!!! It makes a HUGE difference!
I don’t know what to believe anymore. Not more than 2 or 3 weeks ago Marketwatch gave the opposite advice – make sure air filter is clean and tires properly inflated and now CNN Money is saying they are myths?
I don’t know what to believe anymore!
Good question, Star for you.
Hey here’s some answers I have learned about these:
#1Most pumps are buried so deep under ground, that their temperature stays constant all the time no matter the weather, and it’s buried under cement, so it’s fairly chilled fuel.
#2
True.
#3
Following the owner’s manual will keep knocks out of the engine, and keep it performing well.
#4
True
#5
Most A/C’s are electrical now, and don’t pull from the gas burning.
But, windows down at high speeds cause resistance and burn more gas.
#6
Myths. these are for cleaning the sediments in the fuel tank, which in turn causes your gas to burn more efficiently, not less.