By Paul Abelson
senior technical editor
In ads for Freightliner’s new Cascadia and International’s ProStar, there have been contradicting claims about aerodynamics and fuel efficiency. Who’s right and who’s wrong? Is one – or are both – of these big truck makers fibbing to us?
Freightliner officials say they tweaked their tractor during 2,500 hours of testing in their own wind tunnel, a facility designed to test a full-size tractor or chassis cab. They claim 7.8 percent less drag than the ProStar, resulting in 3 percent better fuel economy.
International claims a 9.4 percent reduction in drag and a 4 percent mpg advantage versus Cascadia. International went to the Goodyear Proving Grounds in San Angelo, TX, to conduct independently supervised SAE/TMC Type III fuel economy testing. They claim that the ProStar got 5.7 percent better mpg than Cascadia at a steady 65 mph.
So which company is right? What’s the real story? And how does this affect you as a potential buyer?
To find out, I asked Richard Wood, president of SOLUS – Solutions and Technologies LLC, a research and development company. He and I served on some TMC and SAE panels together. Rick is recognized as an expert in aerodynamics.
He said, “They’re both right.”
“Huh?” I remarked. “What does that mean?”
He explained that aerodynamics is an increasingly important factor in reducing energy consumption as speed increases above 50 mph. The test results are highly dependent on test conditions. Having visited both Freightliner’s wind tunnel and Goodyear’s test track for an SAE/TMC test, I understood what he meant.
Freightliner’s wind tunnel has a fixed box representing a standard trailer. This holds down size and cost, and lets Freightliner concentrate on tractors only, eliminating variables of differing trailers. International used a full-size aircraft wind tunnel in Canada. They claim tests with a 28-foot trailer factors in wake formation, a real-world condition.
Both companies ran independently supervised tests and presented accurate results under different test conditions. So it’s a draw. Remember, aerodynamics is just one of many things to be considered when buying a new truck.