Posts tagged ‘fuel’
Air Conditioning Affects Gas Mileage
By Chad Upton | Editor
In most cars, the air conditioner’s compressor is powered by a drive belt on the engine. When the air conditioner is activated, the compressor adds resistance to your engine. That extra resistance means your engine requires more fuel to turn at the same speed.
In other words, using your air conditioner burns more gas than not using it. Modern cars have very efficient air conditioners, but this truth still stands.
On a hot summer day, you have to keep cool. Does that mean it’s more fuel efficient to drive with your windows down?
Yes and no.
The Society of Automotive Engineers performed a study that examined this question in detail. They performed wind tunnel and track experiments comparing a car and an SUV. With the windows down, the car was half as efficient at 50 mph (80 km/h) than the SUV’s at 30 mph (50 km/h). It’s clear that driving the car with windows down has a dramatic effect on fuel economy, but it affected the SUV even more, especially when a 10 mph (16 km/h) crosswind was added in the wind tunnel.
Consumer Reports found that below 40 mph (65 km/h), drivers are better off with their windows down and air conditioner off.
Jason Toews from GasBuddy.com found at speeds above 45 mph (70 km/h), “wind drag becomes an issue.” He says, “Drive at speeds over 55 mph with windows down and you’ll decrease fuel economy by up to 20 percent or greater.”
Myth Busters has also looked at this issue on a couple occasions. The first time around, their methodology was flawed, so they tried it a second time. The second time, they came to the same conclusion as Consumer Reports and GasBuddy, that windows down are more efficient than running the air conditioner at speeds less than 45-55 mph (70-90 km/h) and the drag at higher speeds makes the air conditioner the more efficient option.
Of course, results vary by vehicle.
There are many factors other than windows and air conditioning that affect fuel economy: drive train, power-train, body aerodynamics and tire rolling resistance. If you want to know exactly how it affects your car, you might try experimenting for yourself. Some cars have a driver information center that displays fuel economy, otherwise you could order an after market product, such as CarChip Pro ($75-$85), which may help you get that data. If you’re interested, some of these are explored in more detail in another post, The Ideal Vehicle Speed for Best Fuel Economy.
If it’s hot outside, you should probably start with your windows down anyway. This gives your air conditioner a bit of a break by clearing the extremely hot air out of the car first.
Do prefer windows down or the air conditioner on?
Broken Secrets
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Sources: SAE (PDF), MythBusters (Ep 22, Ep 38), Edmunds, Bankrate, Consumer Reports, Missouri Gov
Photo: Tomás Fano (cc)
Start Your Lawn Mower in One Pull
If your mower is hard to start or runs rough, this secret is for you.
I get a lot of these secrets from my dad and he gave me this one last spring. My mower ran a little rough and it took a couple hard pulls to get it going. Within a few starts after this secret, it was starting with one easy pull.
The secret is pretty simple: use premium gasoline!
I know what you’re thinking, “I’m not made of money!” But, this is a very affordable experiment to try. In your car, it costs significantly more to use premium fuel, so you’re probably not going to use it unless you have a high performance car that requires it. But, the fuel your lawn mower burns might only cost a few extra dollars per year for premium.
The benefits to your mower are as easy as 1, 2, 3:
- Starts easier
- Runs smoother
- Lasts longer
The proof is in the pull. Now that it starts easily and runs smoothly, I know it’s going to last longer and that’s worth a few more dollars per year.
The same applies to your car. If your car engine runs rough, you should give mid-grade or premium fuel a try. Your engine may sound noticeably better, idle smoother and start much easier too. If not, then it’s a waste of money.
In fact, the FTC says that premium fuel is a waste of money unless your car requires it or runs rough without it. If neither your mower nor car engine improve with premium fuel, then stop using it.
Broken Secrets
Written By: Chad Upton
Photo: yewenyi (cc)
Sources: Louisiana.gov, FTC
The Gas Arrow
Rent, borrow or commandeer an unfamiliar car and you’ll need to gas it up eventually.
You know your own car like the back of your TV remote, but you’ve got nothing on this car. The gauge is near empty when you realize you have no idea which side the gas cap is on.
You’ve got a 50/50 chance, so you wing it. Unfortunately, there’s nothing that says, “this ain’t my car” better than stopping on the wrong side of the pump.
That’s why they invented the gas arrow. Look for the arrow on the gas gauge, it points to the side of the car where the gas hole is.
Of course, not all cars have this arrow. Some people will also say that the pump icon indicates the side of the gas cap with the pump handle, but that’s not universally true.
My Dad shared this secret with me a few years ago. I shared it with a few friends, some of them shared with a few friends and if all goes well, everybody will know about the gas arrow and other little known facts. That’s what this site is all about.
Broken Secrets
Written By: Chad Upton
Source: My Dad
The Ideal Vehicle Speed for Best Fuel Economy
The precise number varies by car and environmental conditions, but the sweet spot is generally between 40-60 mph (65-95 km/h). Most small and medium size cars get the best mileage at about 50 mph (80 km/h).
A lot of factors affect the fuel economy of your car. Some of them don’t vary much with speed, such as the resistance of the engine pumps and accessories. Other factors, like the size of the frontal area and the drag coefficient create increasing resistance with speed.
The faster you drive, the more energy is needed to overcome the aerodynamic resistance of the car. Up to 40 mph, that isn’t really even a factor. So, if you’re driving a box then your best fuel economy is likely closer to 40 mph than 50. If you’re driving a teardrop shaped eco-car, then you’re likely closer to 60 mph. Of course, engine size and other factors are involved too. (more…)
Locking the Gas Pump Trigger
UPDATE: It is illegal in some places to leave the gas pump while filling your tank. After doing some further research, it appears this is done for two reasons. 1. To prevent you from getting back in your vehicle, which can cause a static buildup that could cause a spark (and fire) when you touch the pump handle again. 2. To ensure you are nearby if the auto-stop fails and fuel begins to spill. So, even if your station provides a locking mechanism, the safest option is to hold the handle while filling.
If you’re like me then you like to lock the fuel pump trigger so you can clean all the garbage out of your car while the tank is filling.
Some gas stations remove the device that locks the trigger so you can’t walk away from the pump while it’s filling. But, there is a secret to locking the trigger without the built-in mechanism: stick your gas cap under the trigger.
That’s it. Now you can do other things while your tank is filling, like tidy your trunk or complain about gas prices with some sucker who is attached to their pump.
Keep an eye on your pump and use this tip at your own risk.
Broken Secrets 