The light and space of the Texas prairie around Dallas can zap a trucker’s brain — especially on a crisp fall morning at the end of a months-long drought. The landscape is a dull, bleached-out tan every way you look.
If I throw a glance over to my right-hand rear-view mirror, I can see the Dallas skyline hovering in the distance behind me. I’m heading south now, on Interstate 45, straight into the famous Texas hill country to put my new rig through its paces and find out if the Big Bore 15-liter pounding away in front of me will deliver the goods. So far, this new MaxxForce 15 diesel is performing as advertised as it powers my 77,000-pound gross with relative ease.
A lot of people in those cars are checking out my tractor when they roll past. It is one sharp-looking truck with a gleaming orange-and-charcoal paint scheme.
To most of the four-wheelers, the ProStar+ is simply what passes for a conventional style tractor these days. Truckers with a more practiced eye will note immediately that this is an extremely “slippery” design. True, it pays definite homage to the great International conventionals from years gone by. But the sharp edges and flat surfaces that defined many of those older designs have been replaced by smooth, curved fenders, grille and hood. In fact, all the edges across the front and sides of the tractor have been aerodynamically optimized, giving the ProStar+ a distinct aerodynamic boost.
Aaron Tennant is president and CEO of Tennant Truck Lines out of Orion, Ill. His company runs ProStar+ tractors as their standard spec vehicle and he says his drivers’ experiences closely mirror my own impressions. “Our drivers like the ride and how quiet the truck is. They also give it very high marks for the interior styling, comfort and room,” he says. “It’s a very quiet truck. And as the company owner, I like them for their fuel economy. We’ve tested them against other trucks and found that the ProStar+ delivers about three-tenths of a mile per gallon better fuel economy than other models.”
During the pretrip, a quick unfastening of the fender latches and a gentle tug on the handgrip integrated into the top of the chrome grille is all that is needed to open the hood and check out the 15-liter MaxxForce. This is the engine naysayers said International couldn’t pull off: a 15-liter beast forged in the company’s Huntsville, Ala., engine plant, combining the lower components, such as the block and camshaft, from Caterpillar’s C-Series family of diesel engines with International’s high-pressure fuel injection system and sophisticated electronic engine control systems. This is an exhaust gas recirculation-only engine — meaning there is no diesel exhaust fluid tank or exhaust aftertreatment system. International uses “heavy EGR” to burn off NOx particulate matter during the combustion process by recirculating exhaust gases back into the combustion chamber. Access to all the major engine systems — antifreeze, power steering fluid, engine oil and so on — is a snap.
At a glance, there’s not much going on visually to tell you there’s a MaxxForce 15 under the hood of this ProStar+. True, there’s a chrome badge on both sides of the engine cowl, but it’s understated. But if you look right in front of the A Pillar, you’ll see a 3-inch-long body insert with a faux air vent inserted between the engine compartment and cab. This filler is necessary because the 15 is 3 inches longer than the MaxxForce 13 engine: This is your strongest visual clue that the ProStar+ passing you on the left has a big bore engine under its hood.
Two-stepping through Texas
Up in the tractor and out on the road, the ProStar+ continues to impress. This model features International’s deluxe trim package, so the rich smells of plush leather seats waft over you as you slide behind the driver’s seat. The warm tones of wood panels and trim accent the well-lighted switches on the instrument panel, Itself highlighted by the middle console, which features International’s top-of-the-line stereo and GPS navigation system. Everything is within easy reach for the driver. And the stereo/GPS system is intuitive and quickly mastered.
International’s engineers have done a great job making the driver feel like he’s integrated into the overall design of the vehicle. And everything, from the instrumentation, switch placement, views over the hood and to the sides to the tight, responsive way the truck handles rolling down the road reinforces this feeling.
Another strong positive is the sound insulation in the cab. It’s clear that International designers worked hard to create an integrated, complimentary sound-dampening system that isolates both vibration coming up through the vehicle frame as well as wind, engine and highway noise. Of course, it doesn’t hurt that the MaxxForce 15 is an inherently quiet engine to start with, thanks to its compacted graphite iron design — lighter, stronger and quieter than conventional cast iron used in engine blocks.
This particular MaxxForce 15 is mated to an Eaton 13-speed manual gearbox — and believe me, that big engine gets the rig going fast: But once at cruise speeds, the MaxxForce 15 settles in at around 1,200 rpm and stays there. Even the occasional long climb up a deceptively shallow-looking Texas grade didn’t rile it up: In this environment, downshifting becomes optional for drivers: You can grab a lower gear if you want. But there’s really no need. The MaxxForce 15 might lose 4 or 5 mph starting up the rise, but by the time you’re halfway up the slope you’ll be right back on your target speed. And by the time you reach the top, you might find you’ve even gained a few mph, depending on how steep the grade is.
That won’t hold true in more extreme terrain, of course. But it’s solid evidence that this engine has the on-demand power to make a driver’s life a lot easier if the countryside will allow it.
After some incredible beef brisket at a truckstop north of Buffalo, it was time to turn the big ProStar+ back toward Big D and wrap up the test drive. My main takeaway for the day was a true appreciation for the overall MaxxForce 15/ProStar+ package. This is a truly integrated design, and the solid feel behind the wheel is a direct result.
International would be the first to admit that a 15-liter diesel isn’t for everybody. But if your application demands one, they’ve certainly got an engine that fits the bill. It’s got plenty of power when you need it but cruises as quiet as a kitten when brute force isn’t required. It’s a solid engine mounted under the hood of a solid tractor.
ProStar+ with MaxxForce 15 specifications
Model: PROSTAR+ 125 6×4
Engine: MaxxForce 15, 450 horsepower, 1,550/1,750 lb.-ft. torque at 1,000 rpm
Engine compression brake: MaxxForce for MaxxForce 15 engines
Transmission: Fuller RTLO-18913A 13-speed manual with double overdrive and internal lube oil pump
Clutch: Eaton Fuller Solo Advantage self-adjusting, two-plate, cast angle spring; ceramic, 15.5-inch diameter, soft rate damper, 1,860 lb.-ft. torque capacity with hydraulic actuation with air assist
Driveline: Dana Spicer SPL250XL plus SPL170XL inter-axle shaft
Brakes: Bendix Antilock Brake System, full vehicle wheel control system (four-channel) with automatic traction control
Front axle: Meritor MFS-13-143A wide track, I-beam type, 13,200-pound capacity
Rear axle: Meritor MT-40-14X-3CFR single reduction, 40,000-pound capacity, Amboid gearing in rear drive axle
Front wheels (optional): Alcoa Durabright XBR aluminum disc front wheels, with vendor-applied treatment
Rear wheels (optional): Alcoa Durabright XBR aluminum disc rear wheels, with vendor-applied treatment
Fuel tanks: (two) Top Draw; polished aluminum, 26-inch diameter, 140-gallon capacity with dual supply and return lines
Fifth wheel: Fontaine SL4LWO775012 12-inch slide, 7.75 inches above top of frame, left side release
Color: International Chassis Code 08 (orange/metallic black)
Miscellaneous: Improved sound insulation package and thermal value for sleeper compartment under hood for sound abatement; National Seating HP model driver’s seat with air suspension, high back, two-arm rest, isolator, 8.5-inch adjuster, three-chamber air lumbar
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