Brand Building | TRUCK REVIEW – ProStar

Can International rebuild its brand in the face of stiff European and American competition? – Words by Brenton O’Connor

Following our earlier evaluation of the ProStar in day-cabin version, configured as a rigid tipper and dog trailer application, PowerTorque is back behind the wheel of a sleeper-cabin version, putting it through its paces on a B-double run from Sydney to Melbourne, via the Hume Highway.

The truck was loaded to near maximum legal weight (without any concessional mass management weights) at 62.04 tonnes, which provided an opportunity to test the vehicle on the rather demanding Hume Highway. The route provides plenty of steep climbs and downhill runs to fully test the fuel economy and to get an idea of the performance over a sustained journey.

The ProStar was coupled to a set of tautliner trailers at near full height, to replicate to as near as possible typical operating conditions this truck would encounter in the real world.

As mentioned, the ProStar tested was the sleeper-cabin version. International offers two sleeper-cabin alternatives – the extended-cabin option, ideal for tippers and the like, and the 40” integrated sleeper cabin with extended roof height. This truck and cabin configuration has been setup to allow the ProStar to tow most 34-pallet B-double trailer sets, and, as with other conventional trucks, a 36-pallet combination will require a cabover truck.

Like the T610 Kenworth and the Western Star 5800, the ProStar features a set-back front axle of 1260 mm, bumper to centre of steer axle. This enables the benefit of increased driver comfort through longer front springs and better turning circle; although, more critically, it allows better weight distribution. By comparison, with other models such as the Freightliner Coronado 114 with its extreme set-forward front axle, it is difficult to get the weight forward to load to a legal maximum of 6.5 tonnes.

The ProStar 40” sleeper is very comfortable inside with full walk around ability, which extends to the driving compartment as well as the sleeper – similar to the FXB Western Star. This means you are able to stand up from the drivers seat to move into the sleeper cabin. There is plenty of headroom, and even my 6’4” height wasn’t a problem. The mattress is a thick inner sprung design, and, despite not sleeping on it, it did look comfortable.

The interior is very plain looking, and doesn’t feature woodgrain dash trim, as you would typically see on other American trucks such as Kenworth, Freightliner and Western Star. As such, it’s relatively bland from a visual perspective; however, it functions well, and much to my surprise the build quality seems high. For example, apart from the ashtray/cupholder, there were no rattles or squeaks from the cabin at all, even over rough roads. The doors have an excellent feel when opening and closing, and the door seals work well, so there is no outside air noise entering the cabin.

The seats are the American GRA-MAG brand and are leather wrapped as standard, which is a nice touch. However, the seat cushion is very hard and noticeable on long stints behind the wheel. The backrest is very supportive, and, as such, no back pain was noticeable on the trip from Sydney to Melbourne.

Amongst the standout features (fitted as standard to the ProStar) was the new touchscreen infotainment system. This unit included truck-specific navigation, digital radio, AM/FM radio and Bluetooth audio streaming, which in this day and age should be included on all trucks. Also impressive were the LED headlamps, which provided excellent white light output, making nighttime driving not only easier, but also much safer.

The ProStar under evaluation was powered by the Cummins X15 AdBlue engine, which had been uprated to 600 hp/2050 lb-ft torque, and matched to the Eaton UltraShift PLUS transmission.

This engine and transmission option now comes under what Cummins calls “ADEPT” technology, which provides improved communications software between the engine and transmission.

The engine will de-rate its horsepower and torque level when running on flat ground, in order to save fuel when maximum power is not required. At highway speeds the UltraShift PLUS changes gears and operates as well as any European box, but I still find them frustrating when lifting off, as they are very slow to upshift and typically rev out to 1900 rpm before upshifting. As such, I typically have to manually intervene and hit the up button to force the transmission to upshift. That said, once past about eighth gear the transmission works really well.

Like many of the current European gearboxes, the Cummins/Eaton partnership includes an eco-roll function, which means truck will go into neutral and coast when cruise control is selected and there is no demand for either power or braking on the engine, with the aim to save fuel. Another very handy aspect of the engine/transmission setup is the auto engine brake function, which brings on the engine brake when a speed of 3.0 km/h over the preset cruise control speed is selected.

The cab interior is very quiet, both when the engine is pulling under full load and when on cruise control at highway speeds. It’s the quietest American conventional truck I’ve driven, which makes the job out on the highway driving less tiresome. The truck is noisy on the engine brake though; however, I believe that’s just in-cabin noise and not outside, as the Cummins-sourced exhaust emissions treatment unit is common to all trucks using this engine as it features the exhaust catalyst for the AdBlue injection.

The low interior noise levels were helped by the rear axle diff ratio which, at 4.11:1, helps bring down the rpm at 100 km/h, thus reducing engine noise, and, more importantly, lowering fuel consumption.

On the trip from Sydney to Melbourne an overall fuel figure of 57.8 litres per 100 km (or 1.73 km per litre) was impressive, especially as the truck was loaded for 100 percent of the trip and also had to cope with peak-hour traffic on Melbourne’s Monash Freeway.

Thanks to the set-back front axle and Hendrickson airbag rear suspension, the ride quality is very good, as is handling, and the truck felt both safe and secure when cornering through roundabouts and the like. The truck sits on the road well, and it’s certainly not a chore to keep it within the confines of the lane markings. The steering has an odd feeling when doing sharp turns, such as into a service station, which could be due to the complicated universal joint setup extending from the steering column to the steering box.

An overnight at the Caltex roadhouse at Holbrook was a reminder of the constant challenges facing B-double drivers – the lack of parking for 26-metre-long combinations.

The new service station, which was very impressive and featured a number of food outlets, was let down by the lack of parking for B-double combinations. Due to the peak rush of the Hume Highway in the evening, half an hour was wasted waiting for a park to become available prior to getting a meal and parking up for the night. More work is needed by both government and roadhouse operators to provide more parking spaces for long combinations.

The ProStar is a very impressive package and certainly exceeded my expectations. The truck is quiet, comfortable and rattle free, which, although it sounds basic, is not a claim that applies to all the American truck manufacturers. In essence, those looking for a North American conventional truck would be wise to take a closer look at the ProStar, as, provided the pricing is right, it’s a well spec’d truck that’s suitable for a variety of applications.

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