Road test: Peterbilt 389 turns 379 up a notch

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DENTON, Texas – Brand evolution can be a rocky road for the manufacturer. First, there is the perception that change is a fundamental aspect of retaining relevance and to remain the same is to stagnate. As competitors’ products evolve stylistically and technologically, the pressure to maintain a fresh image and a technological edge mounts, pushing everyone toward new news. Then too, the decision to make changes may be driven by regulatory demands, always a good time to make changes that will fold style and technological upgrades into the overall new product. So it is with Peterbilt’s new 389, the model replacing the legendary 379.

While traditionalists scoff and wring their hands at changing a flagship product, even the most diehard 379 aficionado will find little to complain about in the 389. Yes, there are changes, and the most noticeable of them tend to be in response to EPA ’07.

But the truck is only slightly different in appearance either inside or out. The changes are improvements, to be sure, and attest to the ability of Peterbilt engineering to turn regulatory lemons into marketing and performance lemonade. The necessity for change dictated by EPA ’07 means that cooling capacity had to be added, for one thing.

For another, the attendant loss in fuel efficiency demanded a compensatory response.

Kevin Gustainis, director of fleet and vocational sales, says the only drop in fuel mileage will be caused by the mandated use of ultra low-sulfur diesel due in pumps near you sometime in October of this year.

Like plenty of government initiatives, however, the availability of ULSD is a question mark and the rule actually states 100% availability is not required until Dec. 1, 2010 in the lower 47, while California and Canada have had to comply at the refineries since June 1, 2006.

Gustainis adds, “We expect a 1% drop in fuel mileage with the new fuel.”

Be that as it may, aerodynamic and under the hood changes have allowed for your new 389 to do the same work, and still look real good. Fuel mileage will drop only by the aforementioned 1%. Peterbilt has taken the opportunity afforded by the need for increased cooling capacity to make enough styling changes to change the number from 7 to 8 and give you an even longer hood in the process.

The BBC has increased from 127 inches to 131. The added four inches are in the hood, where the radiator has gotten bigger and the fan is now attached to the engine block rather than the radiator cowling.

This allows the fan much closer clearance to its shroud and increases cooling efficiency. Whether BBC as well as wheelbase influences ride is open to question but a wheel cut of 50 degrees certainly makes the 389 perform well for its size despite the longer hood.

Visibility is not appreciably different, meaning you still need to be careful looking at crosswalks and when stopping behind four wheelers.

Along with these changes a few minor aerodynamic changes have cut air drag by 4%. Gustainis says this reduction in drag will increase fuel mileage, effectively compensating for the loss of mileage from regulatory changes.

The leading edge of the hood has been beveled ever so subtly. And the cutting edge headlights, which Peterbilt says are over 230% more effective, have been styled to look retro-sharp and give little resistance to air flow. The mirrors are aero style and even the hood ornament has been redesigned to reduce drag. But do not fear. The 389 still has plenty of chrome.

The stacks are still ego boosters and still provide blind spots when backing, but we’re all willing to take the visibility hit to shine and sparkle in the parking lot.

I left the Denton factory just in time to hit Dallas traffic. By then I had taken notice of the new Lexus interior and the dash, which is chock full, as you might expect. New in the 389 are a diesel particulate filter gauge, which lets you know when your filter needs cleaning, a very snazzy driver information center with a rheostat style knob to find its myriad features, including real-time fuel mileage and sweet spot indicators. Gauges are well placed and the steering wheel can be adjusted to provide comfort and a good view of the gauges.

The comfort and visibility factors became obvious after the 400 miles I drove the first day, out to Mineral Wells and then south toward Austin. Fit and finish are consistent throughout with the luxury one expects from a premium truck.

It is a fact of a truck driver’s life that his machine can make or break him. Comfort is necessary but performance in every type of environment remains paramount. In traffic grossing 40 tonnes and 70 feet of length, it is awfully nice to have the power and quickness to respond as traffic patterns change. This fact is often overlooked in the big hood segment where folks are primarily interested in super slab up and down performance.

The Cummins ISX 565 in this 389 will give you the best of both worlds. It is aptly joined with the Eaton Fuller 18-speed.

A big truck in heavy weight applications can save tires and other components from the torque of taking curves at slow speeds with those split gears at the bottom, available only in the 18-speed configuration. They are helpful in slow moving traffic as well.

On the big road, the 565 responded extremely well. It has aggressive acceleration throughout the RPM range and plenty of grunt at the bottom end.

In the hill country below I-20, headed for Austin the 389 proved agile and Cadillac-like. It has the feel of a big touring road car, loping through the sagebrush country, looking for something to climb.

I made my flip at Austin and headed back to Denton next day. The Interstate was crowded and the 389 took the challenge easily. Despite its huge hood and long BBC, it is a nimble truck, a confidence-inspiring truck.

I used 125 gallons of ULSD in 600 miles on a truck that had 650 total miles on it when I turned it in. This consumption will rise as the motor breaks in and the 18 speed will loosen up enough to make the occasional need to select a gear smoother.

This truck is well put together and the compensations built into the model change make noticeable performance and comfort upgrades.

Far from being a model change to mask regulatory necessity, Peterbilt has kept the best of the old and added new features that will make buyers happy the 7 changed to an 8.

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