6 gas mileage myths

[Blake]

People care about fuel economy, but they're misinformed about how to actually achieve it. The federal government's fueleconomy.gov site (very useful to check cars' mpg) just published the "Top 10 Misconceptions About Fuel Economy."

Here are a few big myths:

It takes more fuel to start a vehicle than it does to let it idle.
People are really confused about this one and will leave a car idling for half an hour rather than turn it off and restart. Some kids I know started an anti-idling campaign in the suburbs and are shaming parents into shutting down their cars.

Idling uses a quarter- to a half-gallon of fuel in an hour (costing you one to two cents a minute). Unless you're stalled in traffic, turn off the car when stopped for more a few minutes.

Vehicles need to be warmed up before they're driven.
Pshaw. That is a long-outdated notion. Today's cars are fine being driven off seconds after they're started.

As a vehicle ages, its fuel economy decreases significantly.
Not true. As long as it's maintained, a 10- or 15-year-old car should have like-new mileage. The key thing is maintenance -- an out-of-tune car will definitely start to decline mileage-wise.

Replacing your air filter helps your car run efficiently.
Another outdated claim, going back to the pre-1976 carburetor days. Modern fuel-injection engines don't get economy benefits from a clean air filter.

After-market additives and devices can dramatically improve your fuel economy.
As readers of my story on The Blade recall, there's not much evidence that these "miracle products" do much more than drain your wallet. Both the Federal Trade Commission and Consumer Reports have weighed in on this. There are no top-secret 100-mpg add-ons out there.

Using premium fuel improves fuel economy.
You might as well write a check to BP if you believe this. Only use premium if your car specifies it.

http://green.yahoo.com/blog/daily_green_driving/62/six-gas-mileage-myths.html

Not sure what the "vehicle needs to be warmed up" has to do with fuel economy, but good to know

[PM5K]

Not sure what the "vehicle needs to be warmed up" has to do with fuel economy, but good to know

Obviously if you think your car has to be warmed up before driving off you're going to kill your fuel economy for no reason.

[Blake]

Obviously if you think your car has to be warmed up before driving off you're going to kill your fuel economy for no reason.

yeah I guess that would be it.

Just never heard of that as far as fuel economy. Ive always heard that not warming up the car for a few minutes during the winter can hurt the car's engine.

[mrsmaalox]

I've always thought that, aside from the condition/type of car, the main variation of gas mileage is from the condition/type of tires.

[Dex]

I've always thought that, aside from the condition/type of car, the main variation of gas mileage is from the condition/type of tires.

That has a lot to do with it, as does the tires being properly inflated. Lots of other things factor in.

Is it highway or city-driving? Are you stalled in traffic half the time? Are you driving aggressively or leisurely? Is the AC blowing full blast? Is there a lot of weight in the car/trunk/back? Is the tailgate down?

All of these things can noticeably affect your mileage, and several of them will add up.

[Cry Havoc]

Vehicles need to be warmed up before they're driven.
Pshaw. That is a long-outdated notion. Today's cars are fine being driven off seconds after they're started.

THIS.

I have been in so many heated arguments with people about this. They just don't understand modern engines. :pctoss

My mother still clings to the idea that a car should warm up for 5-10 minutes before driving it in cold weather.

[AnthonyM]

Haha...the only reason my dad and I used to warm up the car before we drove is so that the heater would warm up and blow hot air rather than freeze our asses off for 10 minutes if we drove off as we started...

Worth it imo...

[Nathan Explosion]

That has a lot to do with it, as does the tires being properly inflated. Lots of other things factor in.

Is it highway or city-driving? Are you stalled in traffic half the time? Are you driving aggressively or leisurely? Is the AC blowing full blast? Is there a lot of weight in the car/trunk/back? Is the tailgate down?

All of these things can noticeably affect your mileage, and several of them will add up.

Another thing that factors in is the wheels. People will buy a new car with alloy wheels, then change out the wheels for "better looking" ones that also change the tire size. The size of the wheels is factored into the design of the car. Changing the wheels and therefore, the tire, will alter the gas mileage and performance of the car, and will actually lower the trade value of the car.

Today I had my tires rotated and balanced and they asked me if I was interested in new rims. I just looked at the guy and said, "As long as they're not steel wheels, I'm fine with how they look."

My car has been averaging about 24 mpg all around driving which isn't bad. Once I get a tune up and oil change, it should jump back to the mileage I was seeing before, about 27-29 all around and 33-35 on the highway.

Yeah, my car needs to have some work done, but when I get the time to do it, I'll definitely take care of it.

[Cane]

Vehicles need to be warmed up before they're driven.
Pshaw. That is a long-outdated notion. Today's cars are fine being driven off seconds after they're started.

Depends on the car. Read the manual first especially if you have a performance engine and even moreso if you have a rotary engine.

Performance engines generally need 30 seconds-minute to warm up (until the rev meter stops bouncing around on idle) and then you shouldn't go heavy on the throttle until a few minutes of normal driving.

Not sure how much it affects mileage but taking care of your engine will add miles to its life.

[gaKNOW!blee]

unfortunately my car requires premium gas :-(

[Creepn]

Car performance mods will increase your gas mileage and overall performance of a car. Mods such as a cold air intake and/or a less restrictive exhaust system helps alot just to name a few.

[xellos88330]

I heard that running the AC/Heater reduces gas mileage. Not sure if there is any truth to that at all.

Someone call Mythbusters!

[Nathan Explosion]

I heard that running the AC/Heater reduces gas mileage. Not sure if there is any truth to that at all.

Someone call Mythbusters!

Actually, running the AC will drain your gas mileage from what I heard. I do know that it saps 10 hp from your engine when you run the AC.

[Drachen]

They didn't clear the idle/restart issue up at all. They said to turn off the car if you will be sitting "for more than a few minutes". I have always heard that it varies, but it is a good rule of thumb that if you are going to be sitting for more than 6 minutes, turn off your car. WhoTF thinks that their gas mileage will be positively impacted by idling your car for a half hour??

As far as how warming up your car would impact gas mileage, I guess one could argue (and this may have previously been true) that an engine that is warmed up to proper temperature could have more efficient combustion. I would think a block warmer would do better for this since you have to use fuel to warm up your engine.

[boutons_deux]

Running the a/c compressor definitely takes HP/mileage. Turn on a/c full blast, and off, while idling and feel the difference in the engine's vibrations.

Running a pump and fans to move excess heat from the motor to the passengers is a lot less HP.

[peteee]

They didn't clear the idle/restart issue up at all. They said to turn off the car if you will be sitting "for more than a few minutes". I have always heard that it varies, but it is a good rule of thumb that if you are going to be sitting for more than 6 minutes, turn off your car. WhoTF thinks that their gas mileage will be positively impacted by idling your car for a half hour??

As far as how warming up your car would impact gas mileage, I guess one could argue (and this may have previously been true) that an engine that is warmed up to proper temperature could have more efficient combustion. I would think a block warmer would do better for this since you have to use fuel to warm up your engine.
they should have banned all these dumb people from car driving because these people tend to use the horn more, which subsequently means a bigger cost of gasoline.

[MannyIsGod]

Actually, running the AC will drain your gas mileage from what I heard. I do know that it saps 10 hp from your engine when you run the AC.


Running the a/c compressor definitely takes HP/mileage. Turn on a/c full blast, and off, while idling and feel the difference in the engine's vibrations.

Running a pump and fans to move excess heat from the motor to the passengers is a lot less HO.

Running the AC vs not running the AC with the windows up will lower your gas mileage. Running the AC vs not using the AC with windows down on many modern cars is different, however. It is my understanding that on many modern cars it is more fuel efficient to run the AC than it is to drive with the windows down. I don't know if thats 100% true or not, but thats what I've been told from several sources.

[TIMMYD!]

Running the AC vs not running the AC with the windows up will lower your gas mileage. Running the AC vs not using the AC with windows down on many modern cars is different, however. It is my understanding that on many modern cars it is more fuel efficient to run the AC than it is to drive with the windows down. I don't know if thats 100% true or not, but thats what I've been told from several sources.

I heard that too and I think it has something to do with air resistance.

[Strike]

I heard that too and I think it has something to do with air resistance.

Something I read years ago basically says that the drag created by driving with the windows open hinders gas mileage more than driving with the windows closed and the A/C running. At least at highway speeds. As far as stop and go city driving, I've no idea.

[boutons_deux]

Drag is gas mileage's biggest enemy.

[Blake]

Running the AC vs not running the AC with the windows up will lower your gas mileage. Running the AC vs not using the AC with windows down on many modern cars is different, however. It is my understanding that on many modern cars it is more fuel efficient to run the AC than it is to drive with the windows down. I don't know if thats 100% true or not, but thats what I've been told from several sources.

+1

seems to me that I read the magic speed is around 40-45mph to where A/C + windows up > windows down (no A/C).

[MannyIsGod]

Really, if you live in San Antonio, you don't have a choice unless you like showing up everywhere you drive soaking wet. Use your damn AC.