Debunking 7 fuel-economy myths (vehicle, 2012, air conditioning, sedan)
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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—if off-the-mark—tips that can lead you astray. Below are several common myths about fuel use and gas mileage, and the real stories behind them.
A dirty air filter doesn't affect fuel economy CR said this was the case although their test car accelerated more slowly with a dirty air filter. Well duh. Then what would someone do? They would press the gas pedal more, using more gas to accomplish the same goal. Does CR think people will just accelerate more slowly?
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—if off-the-mark—tips that can lead you astray. Below are several common myths about fuel use and gas mileage, and the real stories behind them.
The biggest fuel-economy myth is the gas mileage the manufacturer tells you the vehicle will get.
That thing about the open windows on the highway not making a difference in fuel economy was news to me.
Not sure I agree with your statement about the biggest myth being what the manufacturer says the vehicle will get. I think that the main reason people are unable to get the MPG figures that are stated on their window sticker is that they just drive too damn fast! If your car is rated at, let's say 40 mpg on the highway, you're not going to get that figure if you go blasting down the highway at 75 or 80 mph. I am just amazed at all of the people who routinely ignore posted speed limits these days, even with gas prices as high as they are. I took my car out on the highway yesterday driving to meet a friend about 70 miles from where I live. The posted speed limit on the highway I was using was 65 mph, which seems pretty reasonable to me. I had the cruise control on my car set at 70. While I was driving 70, nearly every car on the highway was passing me! These people must have awfully deep pockets, or they just don't care about fuel economy to be driving that fast.
I remember hearing on the radio that the best speed to drive on the highway for most vehicles to get maximum fuel economy is around 60-65 mph. When you drive faster than 65 mph, your fuel economy drops off noticeably.
Quote:
Originally Posted by vmaxnc
My only comment:
A dirty air filter doesn't affect fuel economy CR said this was the case although their test car accelerated more slowly with a dirty air filter. Well duh. Then what would someone do? They would press the gas pedal more, using more gas to accomplish the same goal. Does CR think people will just accelerate more slowly?
I almost always get far better gas mileage than the EPA rating. Most often, I can beat the mileage you get with your car, using your car. When I was a kid my grandfather and I did the Mobil Economy Run- bet most of you never heard of it. It was the fore runner to hyper milers. My 4.6 Supercrew, I get 24-25 mpgs hiway all the time. My girls Focus, I get 44-45 hiway 33-34 in town with it. There's more to driving than keeping it outa the ditches.
A dirty air filter is dependent on just how dirty. The capacity of most filters today is 7 times required volume. So that makes for a lot of dirt before it starts effecting the A/F ratios. Unless you drive it on the floor, it can almost be black and caked on before it will effect one of the newer PCMs. Average speed of the air going thru most filters at full throttle is only 7 mph. At hiway speeds it's usually less than 1.5 mph thru the filter. Yeah, I know it doesn't sound right as you see the gases shooting out of the tailpipe at WOT. But make that tailpipe as big as the surface area of the filter and see what ya got.
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—if off-the-mark—tips that can lead you astray. Below are several common myths about fuel use and gas mileage, and the real stories behind them.
A dirty air filter doesn't affect fuel economy CR said this was the case although their test car accelerated more slowly with a dirty air filter. Well duh. Then what would someone do? They would press the gas pedal more, using more gas to accomplish the same goal. Does CR think people will just accelerate more slowly?
No, you will just get less air in the engine. That was their point. The computer is still accurately measuring the air coming into the engine because the MAF is behind the air filter. Think of the gas pedal as an air pedal, as that is really what it is on modern cars. If the air filter is clogged and only 60% of the normal air gets in the car will adjust the fuel ratio properly. Throttle position is only going to be secondarily related... you will usually run richer at WOT, but only minimally so. With an average economy car it is probably very minimally different.
BBBut i thought the Super Hightest Duluxe Gold Supreme gas was better gas than the plain old trailer trash regular gas,besides i read somewhere the super high octane gas gave my car 20 more horsepower and an extra 5 mpg, you mean the oil companies lied to me?
Well they didnt say anything about my every 2000 mile oil changes clean new oil will make my car last forever..
Don't matter to me. Even at 12 mpg in my 79 T-Bird, since work is only a 5 mile round trip and I usually only work 5 days a week, my last tank of fuel went 38 DAYS between fill up's. That's right, more than a month. The 76 Mav I keep in Ft. Worth for an emergency car goes more than three MONTHS between fill up's. That's right, I said MONTHS!! I'm so glad I don't live in a large metro area with a two hour commute every day. My fuel costs in relation to other daily expenses are nil.
I think that the main reason people are unable to get the MPG figures that are stated on their window sticker is that they just drive too damn fast!
I agree. You have to remember that wind resistance increases 4 fold when you increase from 50 mph to 70 mph. While it certainly may be true as some people claim, the engine runs more efficiency at higher speeds, with that increased wind resistance your MPG will suffer a lot more then any minor increase in engine efficiency. When driving on the freeway I keep it under 70 MPH, but I don't do a lot of freeway driving anymore, most of my driving is 50 MPH or under.
Quote:
Originally Posted by stilldriveem
Even at 12 mpg in my 79 T-Bird, since work is only a 5 mile round trip and I usually only work 5 days a week, my last tank of fuel went 38 DAYS between fill up's.
I drive a Honda Civic that get's 30+ mpg and live less then 10 miles from work with no traffic. I fill up every 10 days on average. Sometimes at little as 9 days, and other times 12 days depending on where else I go.
Close windows at high speeds - Don't drive with the windows open unless your keep your speed under 50 mph. Driving with the windows open at highways speeds increases aerodynamic drag on the vehicle and lowers fuel economy.https://www.drivingskillsforlife.com...id=3&Itemid=14
The rule of thumb is to keep the windows down while on city streets, then resort to air conditioning when you hit the highway. Every car has a speed at which rolled-down windows cause so much drag as to decrease fuel economy more than a switched-on AC. As you might expect, however, that milestone speed varies widely from car to car—and in some cases, it may be well north of posted speed limitsAt low speeds, at least, the fuel-economy losses associated with rolling down your windows are minuscule. But as your foot gets heavier on the accelerator, the situation rapidly begins to worsen. That's because drag increases with the square of speed. So when you hit the highway, all that wind whipping through your open windows begins to take a major toll. Even with the windows sealed tight, the majority of your car's power goes toward fighting wind resistance when you're cruising at 55 miles per hour. With the windows down, the engine really starts to strain.
The engineers found that rolling down the windows on the SUV had only a small negative effect, in part because the vehicle's big, boxy shape was already creating a lot of drag. So, from a fuel-economy standpoint, a driver of an SUV will always do better to shut off the air-conditioner. The sedan, on the other hand, has a sleeker shape and a lower drag coefficient. As a result, its fuel economy was noticeably affected when the windows were rolled down at highway speeds; at around 68 miles per hour (the test's maximum), there was barely any difference between air conditioning and nature's cooling. If you were driving the sedan any faster than that, the increased drag would presumably make AC the more efficient option.
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you mean the oil companies lied to me?
clean new oil will make my car last forever..
