Are you someone that likes to get there quickly? Do you find you are constantly pushing the speed limits? My husband recently went on a short trip. On this way there he drove about 75 miles an hour on the freeway. By the time he arrived at his destination, he had used an entire tank of gasoline. This is in a 2005 model vehicle.
On his way back he decided to experiment. He drove 65 miles an hour on the same freeway (granted he was headed north vs. headed south). When he arrived home, he had only used half a tank of gas vs. the whole tank of gas. While I’m sure there are many factors that can affect how much gasoline vehicles use, one of the bigger factors is wind. The faster a vehicle goes, the harder it has to push through the wind. This may be what caused my husband to use less gas on his way home.
Obviously I am not an expert on the science of gasoline powered vehicles, but I am intrigued by this. What do you think? Can you save a significant amount of gasoline by merely driving 10 mile and hour slower? Chime in with your thoughts!
{ 25 comments… read them below or add one }
I don’t about that… but I do know that I saw a story on the news one time about how much gas you can save by not speeding up super quick and/or braking a lot. Interesting that it was a full 1/2 tank difference on his trip.
Oh definately!!! I can get an extra 100 miles by going 65 instead of going 70 or more.
The answer to this question is yes and no. All cars have a “sweet spot” that maximizes gas fuel efficiency. Too slow and your engine is operating inefficiently. Too fast and you are using too much power. The trick is finding that sweet spot. It all has to do with how aerodynamic the vehicle is, how big the front is and how much the car weighs. In general smaller, lighter, more aerodynamic cars will get the best mileage at higher speeds while bigger, heavier, less aerodynamic cars will get the best mileage at a lower speeds. So it’s not a matter of 10MPH slower. It’s a matter of getting as close to that “sweet spot” as possible. Ans yes, I know I’m a nerd but that’s what you get when your dad majored in Physics and would give practical application when helping you with your homework. =)
I believe you are right on that one. I have a car that has it’s sweet spot, which I found. But I think it depends on the car & type of gas you use as well.
MythBusters did a show on this a while back, check it out…
My grandfather was an engineer and he always used to say that the most fuel efficient speed was 55 miles per hour. And I would swear that I read that somewhere.. where exactly I don’t know. On a healthy note, people who weigh less also use less fuel to propel their vehicles… lose weight to save on gas, not a bad incentive!
There are lots of factors that can contribute to gas mileage, including the weight in the car, tire pressure, keeping a constant speed vs. braking and accelerating. use of a/c, windows open/shut, etc. But in general speed is one of the most significant factors affecting mileage. Shelley is right, each car has its own sweet spot. My current car gets its best gas mileage at 70, but it was 55 in my last car, and this one is just a newer version of the last, same model. Go figure.
i heard that for each 5 mph over 60 is equivalent to paying an extra 20 cents per gallon for gas, so i could see that being true!
Hi,
I took a class in grad school about hybrid vehicle design. We actually had a project in the class about optimum vehicle speeds on the highway. From a little bit from what I remember, you would use 25% less fuel slowing down from 75 mph to 65 mph just from pushing less air. Vehicles engines also have a range were they generate alot of power for not much more fuel. Slowing down from 75mph to 65mph could put the engine in that optimal range and might account for the other 25%.
Kristine’s husband
Yea, my husband used to drive his 2005 Corolla 65 when we would go out of town because that was the best speed for gas mileage in that car! It saved us a bunch of money! So true!
I’ve always gone by RPM since this is the actual work your car is doing
Anyways I try to keep the dial at 3 on the highway which translates to 55-65mph depending and no more than 2 elsewhere including accelerating.
http://blog.motorists.org/truth-and-lies-about-fuel-saving-tips/
Agreed! I’ve always heard that 55-60 is the most efficient fuel-usage speed for most cars. Can’t wait until I can get a hybrid someday…!
From Wikipedia:
The National Maximum Speed Law in the United States was a provision of the 1974 Emergency Highway Energy Conservation Act that prohibited speed limits higher than 55 mph (90 km/h). This law was modified in 1987 to allow 65 mph (105 km/h) limits on certain roads.
The law was widely disregarded by motorists. Most states subversively opposed the law, ranging from proposing deals for exemption from it to minimizing speeding penalties.
This cap was intended to reduce gasoline consumption by 2.2% in response to the 1973 oil crisis. However, net fuel savings were calculated by the United States Department of Transportation at 1%, and independent studies found savings as low as half of one percent.
In 1995, the law was repealed, returning the power of setting speed limits to the states.
.-= Noelle´s last blog ..Adams Farms Deal 3/19-3/22 SPRING CHICKEN SALE! =-.
I know my fiance and I kind of do a version of this: we drive from Cincy to Columbus. I drive up at 65 on cruise and use less than a quarter tank of gas. He drives back on cruise at ~75ish and uses almost a half.
It does also depend though: sometimes time is money and well worth burning through to get somewhere that much quicker.
From the NMA website:
Q. Don’t lower speed limits save gas?
A. No, research has shown that the 55-mph National Maximum Speed Limit, which was enacted specifically to save gas, had practically no impact on fuel consumption. This is partly because people do not obey artificially lower speed limits. It is also because the differences in travel speeds that result from unreasonable limits waste gas. Most fuel is used to accelerate to a given speed. Speed limits based on actual travel speeds promote better traffic flow, which reduces the amount of braking and accelerating on our roads. This has a positive effect on fuel consumption.
I can’t give any scientific evidence, just first hand experience that driving slower consistently on the highway saves a very noticible amount a gas, really doesn’t change the time you arrive by much and it is safer.
Leslie,
Yes, driving slower saves fuel. If you slam into a tree (or anything else) you are likely to have less injuries than if you were traveling at a faster speed. However, don’t lose sight of the forest for the trees.
Driving with the normal flow of traffic is far more important to both safety and lower fuel consumption rather than simply driving slower because it makes traffic flow more smoothly with less starts, stops, braking, and acceleration.
One way to improve safety and fuel savings is by INCREASING speed limits to more closely match the speed at which people normally travel at instead of setting them artifically low (to generate ticket revenue). It is called the 85th percentile of speed.
I am that annoying person driving 55-60 on the interstate in the right lane, my car is 15 years old and has 200,000 miles. I can usually make it 300 + miles before I have to stop for gas. I have read, my information comes from reading Car Talk, that cars run more efficiently at 45 + miles per hour, but that more wear and tear happens after you start to drive 65 + miles per hour. I lived without a car for 10 years. This one is the only one I could afford to insure so it has to last a long time. I am not driving slow for the fuel economy, but because of the wear and tear. Driving habits have a lot to do with how much a person is going to spend on a car, and so far I’ve been lucky with mine. It costs me about $800 a year to own my car with gas and oil changes. I also continue to bicycle everywhere and not drive that much, which factors into this cost.
I have seen report that state driving 55-65 MPH is usually the most eff. speed for the best gas milage in your vehicle. However if you read the owners manual that came with your car it will tell you which speeds are best for the car you own since each is designed differently. If I keep me van between these speeds I average great milage but if I get hevy footed or use overdrive I can literally watch the gas gauge drop dramatically. I try to leave earlier so I am not tempted to play lead foot and waste gas that is to expensive anyhow.
I don’t remember where I read it, but I read that the MPG is the optimal when you are driving at 55 MPH. So it won’t work if you drive too slow either.
Unfortunately most of my driving is on surface streets with trips under 20 miles and long red lights. My average speed is around 25 mph and I get around 20 mpg, and this is in a brand new compact car.
This will definitely save some fuel but even better is to take it easy when you first hit the gas from a stop. The faster you accelerate, the more fuel you’re burning. Take your starts S-L-O-W and you’ll save a ton more! There’s even some fuel mileage fanatics who drive barefoot to slow their accelerations down!!
For my car, which is a 2008 Chevy Cobalt I find on the highway I get better gas mileage doing 70-75 (which is about 5-10 mph over the limit). This is not saying that every Cobalt will do that, just mine. It is a 2.2 L engine, 4 cylinder automatic.
If I go the limit or under, the gas tank takes a header….and if I go say 80+ the gas tank takes a header as well. So, I keep it about 70-75 on the freeway and it really makes the gas stretch. Then again, it could be the gas I use as well. I use Shell I don’t visit the pumps much, I use Chevron I see the pumps for fill-ups more often. I might just have an odd little car, LOL.
My DH was an Over-the-road trucker for a year and he always drove at 62mph b/c his paycheck was based on profit of the truck, so money in minus fuel costs. Amount spent in fuel was directly related to his paycheck. 62 mph was the good speed to get the best mileage for diesel consumption.
.-= BrandyK´s last blog ..The drawback to living 55 miles from Publix =-.