The interior of the cab is undeniably handsome, with light and dark grays for the trim and nice wood accents that come with the Limited package. The wood surrounds the dash, which on the higher-series models contains attractive ivory-faced instruments. These are evenly illuminated at night, when the faces seem to darken to a charcoal to contrast with the excellent illumination for the numbers and the gauge pointers.
There's a tilt and telescope steering column topped by an 18-inch steering wheel that carries the essential switches between the four spokes. Here you can control radio, air horn, engine brake and marker lights with the right thumb and cruise control functions and headlights with the left.
An array of warning lights in the panel top and center is complemented by a driver information panel lower in the dash. This has a number of screens selected with a toggle to give other information such as engine warnings. Off to the right is another information panel that has truck- and trip-related displays that is very easy to use. It is ported for a number of additional functions, such as an upcoming navigation system, that were not enabled on this unit. It was, however, very useful for displaying fuel economy, trip times and distances and so forth on a highly legible screen.
Another good feature is the rotary controls for the HVAC system. However, we fumbled with them trying to get the right amount of air. It would be nicer to have a climate set point where you dial in the temperature and the system takes care of you. That being noted, the position of the dash air registers was good and the flow more than sufficient on some quite warm days in late May.
At the base of the wing dash are cupholders – or more correctly giant gulp holders. In the driver's holder, a regular-sized cup of coffee just disappears. A removable ashtray makes for an added holder, too. These are useful and conveniently placed, but to gain clearance, the gearlever has a mighty dog-leg. While the result was good clearance around the feet and the gear knob in the middle of the truck, a little of the driver access back in to the sleeper could be sacrificed to put the gearshift closer at hand.
Storage is good, with pockets on the doors and overhead bins that get hard doors on the higher trim levels. Above these and continuing throughout the cab and sleeper is a high shelf. A center stack over the windshield has a couple of pockets and was originally intended for a CD player stack. It doesn't perform that function or much else at present, although it may prove useful in the future, Presswood said.
The seats are mounted to long slides, allowing for some very big as well as small drivers. I set the seat – an International model by National – several stops from the end of the slides.
The seats are comfortable and feature a wide range of air-controlled configurations such as lumbar and shoulder support. Driving was mostly in two-hour sessions with plenty of breaks, but we experienced no real sense of tiring in the three 10- to 12-hour days.
Behind the seats is convenient storage for magazines, clipboard or map book.
The seats sit fairly far apart so that even with armrests there's a 21-inch pass through. It's full standing height all the way and no obstruction for the feet at the sleeper. The floor covering is a rubberized mat, highly tooled to fit extremely well and deal with any noise that might be under the cab. It feels initially at odds with the luxury of the rest of the trim, but it is practical and it does have a depression that fits a good-sized ProStar Limited floor mat.
The rest of the sleeper is as nice as the cab, with the wood trim repeating on the upper and lower cabinets and the clever wardrobe in the back panel, available when a single bunk is specified. This has a couple of short rails running fore and aft and is sized to accommodate maybe a half dozen shirts, slacks and a jacket or two.
The upper storage at the sides is neat. It is described as airliner storage and functions much like the overhead bins in planes, with doors that rotate down. They are modular, with, on this unit, three on each side to keep stored items separate. Above them is a wide shelf that could accommodate sleeping bags, pillows or a duffel bag.
A hanging wardrobe is on the driver's side with a TV shelf, pull-out work surface and a three-drawer stack facing on the other side. The sleeper is configured to accommodate a microwave on top of the wardrobe and a refrigerator under the worktop.
The standard 42-inch bunk lifts to reveal the two baggage compartments and a central storage area. Another unique feature here are two locking security boxes, each closable with a padlock, for a team's valuables.
The interior is bright, with two large opening windows allowing for ventilation. Some drivers don't care for sleeper windows, but I find them a big safety plus when pulling up at an angled intersection or backing on the blind side.
ON THE ROAD
The first day was pretty much freeway all the way after a relatively late start. Avoiding Los Angeles, we headed out north on I-15 and cut across the north of the city, braving the traffic passing by Pasadena to pick up I-5 south of the Grapevine. Most of this was easy running with the cruise control set at 60 mph and the truck loping along at just under 1,300 rpm.
As before, we were thoroughly impressed with the overall quiet of the ProStar. It wasn't until later that I put the sound meter on it, but when I did, the readings of 66 dB(A) on cruise and 68 dB(A) under full load (45 mph, 75 percent engine rated speed and full throttle) were recorded. Even more impressive was the quietness of the engine brake, or Intebrake. This is the retarder built in to the ISX with three performance levels. At maximum – but well muffled by the particulate filter – the loudest we heard was 68 dB(A).
This is a great tribute to the integrity of the cab and floor sealing. Also, we noted none of the aggravating booming periods some cabs make. At this writing, the ProStar leads in offering a quiet interior. But the new Freightliner Cascadia is claimed to be mighty quiet, too.
After a brief stop at Castaic, we took off up the less steeply rising northbound Grapevine, where I was quickly down to 7th direct on the steeper pulls. At one stage, after a particularly balky, steep section, I dropped to 6th direct, but was able to pull up a half gear before getting to the top. Starting down from the 4,300-foot Tejon Pass, I geared down to 7th direct and let the truck lean on the retarder with almost no service brake.
Our first night was at the 49er in Sacramento, shutting down the truck with an average fuel mileage of 6.0 mpg. This was from a zero at Castaic, just before pulling the long grade, because I failed to get the trip to zero and latch on leaving Ontario. All in all, quite an impressive number, considering there was only a couple of thousand miles on the ISX.
I noted that the trailer gap was a lot larger than we would have liked. Earlier in the day we slid the trailer up a little – perhaps too much, given how heavy this particular tractor was on the front end.
On Day Two, we drove I-5 to Exit 747 and turned off at Weed, Calif., for U.S. 97 toward Klamath Falls. Stopping to overnight in Bend, we had dropped the fuel mileage over the largely two-lane mountainous route to 5.7 mpg. Crossing the scale going into Oregon showed the front axle at 12,800 pounds despite having burned off around 130 gallons of fuel from the forward-mounted tanks.
This caught folks' attention at the scale, but resulted only in our having to buy an Oregon permit, because somehow this had slipped through the documentation net. Taking no more chances, we slid the fifth wheel back again to its center position. To heck with fuel mileage.
Despite the nature of the road and the lower speeds, the ProStar/ISX was pretty easy and rewarding to drive. The ISX pulled strongly, with the good throttle response we have noted since the advent of variable geometry turbochargers. The lower speeds got us into more gearshifting but it was relatively easy stuff.
On Day Three, we ran north to The Dalles, then west on I-84, soft-pedaling or using cruise control and picking up the odd 1/10 mpg so that by the time we cruised in to the Tacoma dealer we were right on 5.9 mpg.
Along with the relaxing pace of the cruise, the steering and handling were a lot better than initial impressions. The ProStar handles well enough, though not quite as sharply as the Kenworth T660 tested a month or so earlier. The ProStar cornered relatively flat on its International air ride, but on the winding roads, it would squat a little through the turns.
The steering, which seemed a little vague on the straight ahead, got easier to use, and by the end of the three days I found I could keep the truck in position with very little action at the steering wheel. The International engineers had told me previously that the TRW gear has been sharpened up for the ProStar, and by the end, I found myself in agreement.
Braking was nicely progressive with good feel and power in low-speed stops.