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Trucker Talk

11 April 2008
Save Fuel - Truck Aerodynamics 101

Save Fuel - Think Aerodynamics 

We often hear the phrase “size matters”.  I won't go into all the potential meanings for that phrase, but I know for trucks that “drag matters”.  Drag is wind resistance and reducing that drag could spell the difference between a profitable run and the break even point. 

Fuel prices aren't going to decrease anytime soon so we might as well start figuring out every way possible to save fuel costs and that means decreasing drag whenever possible 

Proper truck aerodynamics is one way to save as much as 15%- 20% on fuel costs.  At 100,000 miles per year and $4 per gallon fuel that equates to as much as $10,000, perhaps more.  That's real money in your pocket if you are an owner-operator.

How do you do it is the question?  And obviously what follows is, “How much does it cost?”

Lets deal with the “how to” part first -

Trailer side skirts and moving the trailer as close to the cab as possible offer more efficient air flow and decrease the amount of fuel required.  Air tabs on the back of a trailer are also a worthwhile investment.  Flat bed trailers can gain aerodynamic efficiencies just by arranging the tarps to make air flow smoother.  There's a lot of high paid “suits” that are studying truck aerodynamics and we would be smart to pay attention to them, at least in this instance. 

How about cost? 

Costs are hard to find on the Internet – seems that the manufacturers are not saying much.  You can probably bet the cost is going up as the price of fuel goes up.  I did find one site that quoted a cost of about $2500 dollars for trailer fairings.  

How about helping your fellow trucker by providing some info on cost for these add-ons?  The more that price is available, the less we will be charged as companies begin to vigorously compete with each other.  Kinda like that broker thing that we all face! 

Here's some links that might help. 

Freight Wing 
Laydon Composites 

Posted by george wilkins at 10:25 AM  |  LINK to this post  |  3 comment s  |  Subscribe

Here is one thing not generally understood - the power needed to overcome aerodynamic drag increases as the cube of velocity. In other words, it takes 33% more HP to go just 10% faster & to go twice as fast requires 8 times the power! Those numbers are not precise as there are many variables, but they're pretty darn close, as proved @ places like the Bonneville salt flats. On 1 motorcycle we picked up 1 mph just by taking the tachometer off the handlebar - the little things do matter! But you don't need to be setting land-speed-records to see the benefit of reducing aero drag as much as you can & even 1/2 mpg increase @ normal highway speeds will save you a lot! Like an old-style Petercar, KW, etc. with a huge front bumper & big sunvisor? So do I - but a brick aerodynamically & an "Anteater" KW with the same engine & gearing will walk off & leave it. And get better fuel mileage running the same speed under the same conditions. I drove cabovers many years ago & those are really a brick! But although most attention is paid to the frontal area & trying to smooth that out, the air between tractor & trailer, coming off the back of the trailer & especially going underneath is every bit as important. Things like a fuel tank for a reefer & pallets on racks hanging underneath the trailer cause aero drag too. Of course it's not practical to re-design your whole rig even if you had the time & money to do it, but just simple things make a difference & I'd bet if you walked around your outfit you'd see something that could be adjusted or moved, just to cut some air drag down.
Posted by art_njr on April 11, 2008 at 4:43 PM

Art Thanks for the reinforcing words of wisdom. I was just reading a post from a fellow going from Mass to California - ( about 3000 miles). If he slowed from an avg speed of 70mph to 60mph or 65 to 55 he would save about $215 in fuel costs - it would take 7 hours longer, but that is the equivalent to a pay of $30 per hour. Probably worth the extra time.
Posted by george wilkins on April 11, 2008 at 8:08 PM

< I was just reading a post from a fellow going from Mass to California - (about 3000 miles). If he slowed from an avg speed of 70mph to 60mph or 65 to 55 he would save about $215 in fuel costs - it would take 7 hours longer, but that is the equivalent to a pay of $30 per hour. Probably worth the extra time. > There's a cost/benefit ratio that has to be considered & I'm surprised the big company "bean-counters" don't. For example, I drove company trucks with a "fuel-squeezer" Cummins & a 9-speed trans. But with a "4 & a 1/4 Cat" engine & a 15-speed, I could haul @ least 1 more load per week & although the fuel mileage was a bit lower, the increased revenue more than made up for that. For example, I've been up the "Grapevine" in California going 29 mph foot dead to the floor in a co. truck - that's all it would do with the engine & gearing. Saving $$$ ??? Nope - have to run the rig hard all the time to get from point A to point B & one with a better setup will not only do it faster, but cost less in the long run. Running a big diesel engine @ 100% power all the time is not a wise thing to do. And especially when the transmission gear ratios don't allow you to run @ peak torque @ any given speed - peak torque is where you get the best fuel mileage & "pulling power". Not trying to brag, but not only was I a co. driver (Teamster & non-union) & O/O too - over 1.25 million accident-free miles, I'm also an engineer. "Old fart" now & haven't been to college since 1979, but I do know what works, what doesn't & why. Not to say that new things won't be discovered & developed - lots of really smart youngsters out there - but we can use what we already know. If your engine makes peak torque @ 1650 rpm, you need to be @ 1650 all the time, or as close to that as you can get, given the gear ratios you have to work with. And more throttle @ 1600 rpm uses less fuel than less throttle @ 2000 rpm does. And anything you can do to reduce aerodynamic drag will save fuel. Got some neat looking chrome visors on your headlights? Aerodynamically that's a parachute. Yes, the more rearview mirrors the better, but can you mount them so they aren't sticking out in the air so much? Details, details, details - we look for a 10th of a mph racing, but you can save 1000's of $$$ by paying attention to the same details. Just for example, do you know what the tire pressure is in all your tires? Can you tilt that air-dam on the roof of your tractor a little bit to go with the trailer you're pulling? I've picked up 1/2 mpg by doing such things & you can too.
Posted by art_njr on April 12, 2008 at 6:30 PM