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Better Mileage From Your Car
The facts about more MPGs
A look into practical real world solutions for getting the most miles per gallon out of your car, truck SUV or van in a climate of ever-rising fuel costs and for knowing how to choose the right alternative fuel source automobile for your lifestyle.
Driving Behind Semi’s and Big Trucks
Improving Your Fuel Economy – Driving Behind Semi’s and Big Trucks
Drivers tend to adopt an entirely different persona when they are on the highway. What is normally a defensive and considerate driver becomes an impatient, aggressive speed freak who routinely does 10 to 20 miles per hour over the speed limit. Highway driving, to say the least, is both unsafe and taxing on your fuel economy.
Most speed limits of American highways are set at around 60 miles per hour, though there are some freeways and highway systems that have speed limits that are slightly less restrictive. What you probably aren’t aware of is how high speed driving, even when cruising, affects your fuel economy.
High Speed Driving and Fuel Economy – How They’re Linked
Have you ever been water skiing? If so, do you know the sensation of falling? Once you let go of the rope and fall you stop in a matter of seconds, regardless of how fast you were traveling before hand. The water places sufficient resistance that you will come to a complete stop whether you like it or not.
Driving is the same way.
The faster you are driving the more air resistance your vehicle is enduring. When you let off the gas, the engine stops creating thrust and your vehicle begins to slow down. This is more apparent at higher speeds as opposed to slower speeds, and this is the direct result of air resistance (also called wind resistance). Ever noticed how your car slows down faster when you are going faster? That is because the car is facing more resistive forces.
Obviously, the more resistance that is placed on the car the more fuel that will be required to continue operation at a given speed.
Driving Behind Semi’s – How It Affects Fuel Economy
As we mentioned prior, air resistance has a significant impact on fuel economy- this is why you see hyper-aerodynamic vehicles, such as the Honda Insight or Toyota Prius in production. Now, when a larger vehicle (such as a big truck or a Semi) is driving it has to pierce through a lot of air. In the space behind it there will be substantially less air resistance, as the Semi has already plowed through the air .
This phenomenon is called “drafting,” you may have heard this term if you watch automotive racing. Following a Semi at a safe distance is a way to increase your fuel economy as a result of the reduced resistance on your own vehicle. It’s like following in the wake of a large boat; the boat has already chopped through the water, leaving behind it a patch of smooth water.
7 Responses to “Driving Behind Semi’s and Big Trucks”
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Sounds like an awesome way to get in a wreck only to save a few bucks in gas! Following behind a semi means you have zero clue what is happening in front of one traffic/accident/or road hazard wise. (not to mention truckers don’t like cars hanging out in there blind spots)
Obviously, following a technique such as drafting behind a large truck requires extreme care and caution and is not advisable in most, many or all situations. Driver comfort level, road conditions, speed, visibility and tolerance to risk all need to be factored in to whether you want to take a risky circumstance, driving, and make it even more risky.
Drafting certainly does save fuel costs but ultimately you must decide if it is worth risking your safety for.
We, at BetterMileage.org, don’t endorse drafting, but merely present it as one of many ways to cut down on fuel costs on the open road.
Use common sense on the road and stay safe!
Yes, this is bar-none a stupid idea. Holding a rope tied to a car and wearing roller skates is a fun way to skate, but you don’t put that idea on a ‘Learn to Skate’ website and then say, ‘Oh, this is dangerous - don’t do it.’ I feel this tip is here in bad taste.
drafting, what an irresponsibles thing to state. I cannot find the stats right now to back the following claim but…
I read years ago drafting was a farce unless you are within 10 feet of the semi trailer. the aerodynamics rolling off the trailer quickly drop below in a vortex of turbulence I’ve personally felt before, especially in our convertible.
drafting in race cars works because the cards are one to two feet (sometimes less) behind another.
stupid comment.
You tree huggers wanted the speed dropped for semis for what you want to call ‘globel warming’ and now you do ‘ENDORSE’ following too close. I hope you get a ticket, if the driver doesn’t wreck you first. GOOD LUCK
mythbusters just did this and it is effective even at 100 feet and as close as 30 feet can have somewhere around a 50% drag reduction, however if you are inside 10ft there is nearly a 100% drag reduction. its not a terribly stupid idea if you’re a decent distance behind the truck because you will be easily and comfortably able to out-brake the truck.
I have a car with an MPG meter and I can tell you that this works at SAFE following distances. Those trucks are going to be there whether we like it or not, so we might as well get some use out of them. I can pick up 2-3 mpg following a 53′ trailer at around 120 ft at 65 mph. The key is to pick a truck with an aerodynamic body kit. They leave far less wake turbulence. Just follow along and let the low pressure pull you along. BTW, this is proof that trucks suck. Literally. You, if you let them.