Our Summarized Response to International Truck
and Engine Corporation’s Advertising Claims
INTRODUCTION
Recently, International initiated an industry-wide campaign to attempt to convince our
customers that their truck is both more aerodynamic and fuel efficient overall. Our response to
this claim is summarized below.
OUR WIND TUNNEL TESTING AND VALIDATION
International claims that our wind tunnel tests are invalid because we do not test a full tractortrailer.
However, extensive industry testing and computer modeling has shown that the drag
from a trailer’s tail end, or wake, is very similar no matter what tractor is towing the trailer.
International itself only tested with a 28-foot trailer, not a 53-foot trailer. If matching the tractor
aerodynamics with the trailer’s wake is as important as they claim, how could they legitimately
test with such a small trailer? Extensive tests have proven that there is no material effect
between tractor aerodynamics and trailer wake.
Auto Research Center (ARC)
International also questioned the credibility of the Auto Research Center (ARC) who has
validated the results of our testing, stating that ARC is “best known for testing racecars.” We
selected ARC precisely because they have a significant reputation as superb aerodynamicists
and understand vehicle aerodynamics and drag. Far from being “best known for testing
racecars,” these engineers and scientists are experts in the field of aerodynamics and have
extraordinary qualifications to examine how vehicle testing is done.
INTERNATIONAL’S FUEL ECONOMY TEST
We have a number of concerns as to the way International conducted their fuel economy test.
These concerns culminate in our belief that the results of the test are invalid.
Type III Test – The SAE Type III Test International conducted uses a relatively short
testing cycle, around a flat track, at a constant speed, with no engine regeneration, and is not
representative of “real world” driving conditions. We prefer using the longer Type IV test. We
would certainly not make any claim using a Type III test alone.
Third Party Validation – We do not know who the independent party was who performed
the International tests. They hint that Goodyear was, but both Goodyear and the “sponsoring
retailer” have distanced themselves from International’s test. We don’t know who the third
party is, but we would certainly like to talk to them.
Pre-Production Engine Used? – When Detroit Diesel was able to inspect the engines
(one week later) used in the International test, they found that according to the EPA-mandated
engine emissions label on the ProStar engine that it was certified last year with a level of 2.1
grams of NOx. However, since January of this year, newer versions of these engines had to be
certified at a lower 1.45 grams of NOx, which is the current production design parameter for this
engine. We can’t tell from the label whether or not a non-production version of the engine was
used.
Malfunctioning Fuel Return Valve – At the beginning of our tests in Week 2 (after
International’s tests had already been conducted) we discovered the valve on the return fuel
side was not working properly so fuel was not returning to the test tank evenly which could
inflate total fuel usage when measured from the test tank. This had to be fixed before we could
continue with week 2 tests.
Rear Suspension Height Adjustment – The suspension ride height on the Cascadia
was not correct, according to our published suspension specifications, and had to be lowered
by two inches. The incorrect height effectively increases drag because it changes the relative
position of the tractor and leading edge of the trailer top and presents a vehicle with a larger
frontal area.
Non-Optimal Fifth Wheel Height – The fifth wheel height was almost 8 inches on
the Cascadia, well over an inch higher than the 6.75 inch recommended height. This raises
the trailer and produces a larger relative distance between the top of the trailer and top of the
tractor, thus reducing tractor-trailer aerodynamic efficiency.
Recirculation Baffle Missing – The plastic recirculation baffle mounted around the
radiator was missing on the Cascadia. This piece helps to direct wind flow to the radiator and
increases tractor aerodynamics. For some reason, this baffle was completely missing and had
to be installed for the Week 2 test.
We suspect that most or all of these issues noted above existed during the Week 1 testing when
neither Freightliner, Detroit Diesel, nor any third party was present.
FINAL NOTES
1. Cascadia is the most aerodynamic vehicle today. It is more aerodynamic than the ProStar or
any other competitive truck.
2. Our wind tunnel is very accurate and shows the true aerodynamic difference between truck
models. Its results have been validated by a legitimate and respected third party.
3. In light of all obvious flaws in International’s test procedures, and the results from later tests,
we can safely state that International’s claimed fuel consumption advantage will not stand up to
real-world comparisons done by our customers in regular service.