PACCAR MX-13 vs. Mack MP8: Why Engine Weight Belongs in Your Dump Truck Spec Conversation Too

Most engine comparisons in this industry stop at horsepower and torque, and we've done plenty of those ourselves. But if you run dump trucks for a living, there is a spec that gets skipped far too often and matters just as much to your bottom line: how much the engine itself weighs. Every pound sitting under the hood is a pound your GVWR budget cannot spend on payload, and on a truck that gets paid by the load, that trade-off is real money, not a footnote.

So instead of another straight horsepower shootout, let's put the PACCAR MX-13, the engine behind the Kenworth T880 and its new electric sibling, and the Mack MP8, the engine behind the all-new Granite and Keystone, side by side on the numbers that actually decide how much material you can legally haul per trip.

The Weight Number Almost Nobody Asks About

PACCAR's MX-13, as spec'd in the current Kenworth T880 lineup, carries a dry weight of 2,600 lbs according to PACCAR's own published spec sheet. Mack's MP8, the standard engine option across the redesigned Granite and Keystone, comes in at approximately 2,597 lbs per Mack's published engine specifications. Those two numbers are, for practical purposes, identical, a 3-pound difference is well within the kind of variance you'd see between individual build configurations on either engine. Neither manufacturer holds a meaningful weight advantage here, which is itself a useful thing to know before you let a sales conversation convince you otherwise.

PACCAR MX-13 dry weight: 2,600 lbs

Mack MP8 dry weight: approximately 2,597 lbs

Why does this matter at all if the two are basically tied? Because it reframes the real question. If engine weight were a genuine differentiator between these two, it would belong at the top of your spec sheet. Since it isn't, you're free to make the MX-13 versus MP8 decision on the factors that actually do differ: torque delivery, dealer network, and how the truck is built around the engine.

Where the Two Engines Actually Diverge: Torque

The PACCAR MX-13, in its current top rating as spec'd across the T880 lineup, produces up to 510 horsepower and up to 1,850 lb-ft of peak torque, delivered at 900 rpm according to PACCAR's spec sheet. The Mack MP8 covers a broader published range, 415 to 505 horsepower and 1,650 to 1,900 lb-ft of torque depending on rating, meaning Mack gives a fleet slightly more room to tune the engine toward either fuel economy or maximum pulling power within the same base engine family.

PACCAR MX-13 peak torque: up to 1,850 lb-ft at 900 rpm

Mack MP8 peak torque range: 1,650 to 1,900 lb-ft depending on rating

At the top end, the MP8's highest-rated torque configuration edges out the MX-13's ceiling by 50 lb-ft, a real but modest difference. For a dump truck spending its life pulling away loaded from a pit or a demolition site, that top-end torque number matters more than outright horsepower, it's what determines how confidently a loaded truck gets moving on a grade without excessive engine strain or clutch wear.

The Mack MP8 also brings a documented 89 percent torque rise and a 16:1 compression ratio, and Mack's engine brake, Powerleash, is rated at 500 horsepower of retarding power at 2,100 rpm, a genuinely useful number for any dump truck running loaded descents, since strong engine braking directly reduces service brake wear on a truck that is stopping and starting all day.

What This Means for a Kenworth vs. Mack Decision

If you're choosing between a Kenworth T880 and a Mack Granite or Keystone for your next dump truck, the engine weight question is settled: it's a wash, and you should not let anyone tell you one truck hauls meaningfully more payload than the other purely because of engine mass. The real decision comes down to torque delivery preference, at the margins the MP8's higher top-end torque rating and strong engine brake numbers are a genuine plus for steep-grade, heavy-load work, while the MX-13's PACCAR-integrated design and extended 75,000-mile service intervals are a real advantage for fleets prioritizing lower total maintenance touches over the truck's life.

Neither is the wrong answer. Both are proven 12.8-to-13-liter vocational diesels with millions of real-world miles behind them, and both power dump and mixer trucks working demolition sites, quarries, and ready-mix routes across the country every single day. The right choice comes down to which dealer network, parts availability, and duty cycle actually fits your operation, not a marketing claim about which engine is "lighter" or "stronger" in isolation.

The Financing Side of an Engine Decision

Whichever engine you land on, the bigger financial mistake is renting instead of owning while you make up your mind. A rented dump truck builds zero equity regardless of what's under the hood, and every month spent renting is a month you could have been building ownership in a truck your business actually controls. BFC helps contractors move from renting to owning a Kenworth T880 or Mack Granite dump truck without forcing a years-long wait between purchases, unlike lenders who require one truck fully paid off before they'll discuss financing the next.

Related Reading

For the full picture across all four major dump truck engines, our earlier deep dive on PACCAR MX-13, Mack MP8, Cummins X15, and Detroit DD13 compared goes deeper on horsepower and torque across the full field. For chassis-level comparisons, see our

Kenworth T880 vs. Freightliner 114SD Plus and Mack Granite vs. Freightliner 114SD Plus comparisons, and our deep dive into

Mack's MP8 engine and its role across the Granite and Keystone.

Service Intervals: A Real Cost of Ownership Difference

Beyond weight and torque, the PACCAR MX-13's service structure is worth factoring into a total cost of ownership comparison. PACCAR extended the MX-13's oil and fuel filter change interval to 75,000 miles as part of its ongoing engine refinements, and the engine carries a 5-year, 100,000-mile factory warranty on current production units. For a dump truck fleet, fewer scheduled service stops over the truck's working life translates directly into more days the truck is actually earning money hauling loads instead of sitting in a service bay.

Mack does not publish a directly comparable extended-interval claim for the MP8 in the same way, though Mack's own OneCall and GuardDog Connect telematics platform, standard on the Granite and Keystone, gives fleets real-time predictive fault data that can catch developing issues before they become an unplanned breakdown, a different but genuinely useful approach to minimizing downtime. Which approach a fleet values more, longer intervals between scheduled service versus better visibility into unscheduled issues before they happen, is a legitimate factor in the MX-13 versus MP8 decision that has nothing to do with raw horsepower.

Dealer Network Density Matters More Than the Spec Sheet

On paper, the MX-13 and MP8 are close enough in output that a fleet could reasonably choose either and be well served. In practice, the deciding factor for a lot of contractors ends up being something the spec sheet never mentions: which brand has stronger dealer and parts support in your actual operating area. A PACCAR MX-13 only gets serviced quickly if there's a well-stocked Kenworth dealer nearby, and the same goes for Mack and the MP8. Before finalizing an engine decision based on the numbers in this article, it is worth calling your local dealers directly and asking about parts inventory depth and average turnaround time for common MX-13 or MP8 repairs in your specific region, South Florida's dealer landscape for both brands is strong, but that is not universally true everywhere, and it is the kind of detail a spec comparison genuinely cannot answer for you.

How the Broader Engine Field Stacks Up

For context, the MX-13 and MP8 sit in the middle of the broader vocational dump truck engine field. Cummins' X15, available in trucks like the International HX and HV, reaches further at the top end, up to 605 horsepower and 2,050 lb-ft of torque in its highest ratings, real headroom for the heaviest aggregate or quarry work. Detroit's DD13, standard across much of Freightliner's SD Plus lineup, spans a similarly wide 350 to 525 horsepower range on a 12.8-liter block. None of that makes the MX-13 or MP8 the wrong choice, it simply means the Kenworth-versus-Mack decision this article focuses on is really a decision between two closely matched, well-proven options in a field that also includes genuinely higher-output alternatives for fleets that need them.

Cummins X15 (top rating, International HX/HV): up to 605 hp, up to 2,050 lb-ft torque

Detroit DD13 (Freightliner SD Plus): 350-525 hp

South Florida Duty Cycles: Heat, Humidity, and Idle Time

An engine's published specs don't account for the specific punishment South Florida's climate adds to a dump truck's duty cycle. Extended idle time waiting in line at a limerock quarry or a demolition debris transfer station, combined with consistent high heat and humidity, puts real additional strain on any diesel's cooling and emissions systems regardless of brand. Both the MX-13 and MP8 are proven in hot-climate fleets nationally, but it's worth asking your dealer specifically how each engine's cooling package performs in extended-idle, high-ambient-temperature conditions typical of a South Florida summer, rather than assuming national average performance data tells the whole story for your operation.

Resale Value: A Wash, Same as Weight

Just as the weight comparison came out essentially even, resale value between a well-maintained Kenworth T880 with an MX-13 and a Mack Granite or Keystone with an MP8 tends to track closely in the used-truck market, both are proven, high-volume vocational platforms with deep secondary markets and strong parts availability years after the original purchase. Neither engine choice by itself should be expected to meaningfully move your truck's resale value five or seven years down the line, condition, mileage, and documented maintenance history matter far more than which of these two well-established engines sits under the hood.

That consistency across weight, resale, and general reliability is actually the most useful takeaway from this comparison: you are choosing between two genuinely sound options, and the decision should be made on the practical factors that differ, torque delivery preference, dealer proximity, and existing fleet standardization, rather than searching for a clear technical winner that, on the numbers that matter most to a dump truck operator, does not really exist.

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