What We Learned From Maxing-Out Our Chevy Silverado ZR2’s Towing Capacity

From hauling payload to towing trailers, pickups are the workhorses of the automotive world. Trucks are built to do work—it’s one of their core functions—and off-road-focused models aren’t immune. Since we picked up our yearlong review 2024 Chevrolet Silverado 1500 ZR2 it’s spent a quarter of its life saddled to a trailer that nearly maxes out its tow rating. Over the course of more than 2,500 miles of towing, it’s safe to say that we’ve learned a thing or two. Here’s what you need to know.

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You Have To Know Your Numbers

You’ve heard us say before that our Duramax diesel-powered 2024 Silverado ZR2 offers a maximum tow rating of 8,700 pounds. That figure, on the surface, is a decent rating for an off-road-oriented half-ton pickup. By contrast, Ford’s F-150 Raptor tops out at 8,200 pounds, and its Raptor R stretches to 8,700 pounds. Ram’s new RHO will do 8,380 pounds and Chevy’s Silverado 1500 ZR2 tops the class at 8,800 pounds when equipped with the gas 6.2-liter V-8. However, that figure is but the tip of the proverbial iceberg when it comes to towing ability.

Any truck owner who tows needs to be familiar with gross vehicle weight rating (GVWR) and gross combined weight rating (GCWR). Further, they’ll also need to be aware of the vehicle’s actual curb weight. This is where things start to get fun. A truck’s actual maximum payload and tow ratings are functions of simple math equations: gross vehicle weight rating minus actual curb weight equals payload.

We can demonstrate by using our Silverado ZR2 as an example. For 2024, Chevy rates the Duramax-powered Silverado ZR2 with a GCWR of 15,000 pounds and GVWR of 7,300 pounds. Our truck tips the scales at 5,770 pounds, with a full tank of fuel and no occupants. While Chevy says our truck should have a maximum payload rating of 1,550 pounds, when we do the math (7,300-pound GVWR minus 5,770-pound curb weight) we find an actual payload rating of 1,530 pounds. This may seem insignificant, but every pound matters.

Getting to the maximum tow rating is just as direct thanks to the implementation of the SAE J2807 standard test procedure. Each vehicle must pass a battery of trials that includes 0–30 mph and 0–60 mph acceleration, climbing a 12-percent grade from a stop, holding the vehicle on said grade with just the parking brake, stopping with and without trailer brakes, an understeer test, a trailer sway test, and a simulated tromp up the Davis Dam grade—all of which are done at full gross combined weight. When a vehicle passes, its maximum tow rating can be advertised as simply GCWR minus GVWR. For our Silverado ZR2, its 8,700-pound max tow rating is a product of subtracting its 7,300-pound GVWR from its 15,000-GCWR (which is reduced from other Silverado models due to ZR2’s lifted height, softer suspension, and off-road tires).

Though the SAE J2807 test is optional, all pickup manufactures currently adhere to its methods. The test can also be applied to SUVs and vans, but adoption in those classes is mixed.

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It’s Easy To Overload

If you made it through our middle school math lesson, you’re ready for the deep dive into practical application. In the first five months with the 2024 Silverado ZR2 we managed to accumulate more than 1,244 miles of towing and in the past two weeks added an additional 1,382 miles to that figure.

With such a relatively low maximum tow rating compared to the broader half-ton class (for example, a Duramax-equipped Silverado 1500 High Country is rated at up to 13,300 pounds of towing with a 19,000-pound GCWR), it’s critically important that we know the exact weights we’re working with. One thing that we knew before we started towing with the ZR2 is that our 20-foot toy hauler travel trailer tips the scales at about 8,200 pounds, depending on cargo. Knowing the trailer offers a reasonable margin of error, we turned to payload.

Most pickup owners often forget that a trailer’s tongue weight directly affects the truck’s cargo carrying capacity. Often, packing a truck’s bed and cab full of tchotchkes prior to hitching a trailer will result in the vehicle being grossly over its GVWR.

To ensure that we were loading the Silverado and trailer properly we first gathered all the supplies we intended to bring along for our two-week road trip. Then we grabbed our trusty vehicle scales and set to work weighing not only the tongue of the trailer, but also every piece of kit that we intended to load into the bed. We quickly found that the seemingly innocuous pile of gear that included a few camp chairs, propane cylinders, extra diesel exhaust fluid, a box of tools, an extra five gallons of diesel, and an empty wastewater tote added up to 462 pounds. When combined with the nearly 500 pounds of humans and floof in the cab, we were left with only about 588 pounds of payload available for the trailer’s tongue weight.

Complicating the situation was the fact that our trailer checks in with a tongue weight of about 1,000 pounds. While this figure is well within the 10-to-15-percent margin of gross trailer weight that is recommended, loading all the gear into the bed would push us over our payload capacity by 412 pounds. At this point, we opted to move most of the gear into the trailer.

Once underway, we made it a point to roll the whole operation across a certified CAT scale to ensure that we were in fact under our max gross combined weight of 15,000 pounds. When the weight slip printed, we noted a figure of 15,380 pounds. Fortunately, our trailer holds 100 gallons of fresh water, so dropping half brought us just under the limit.

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Does The 3.0-liter Duramax I-6 Have an Exhaust Brake? 

Those familiar with the larger Silverado Heavy Duty and its 6.6-liter V-8 Duramax diesel engine would also quickly recognize the exhaust brake activation button located on the dash. The light-duty 3.0-liter I-6 Duramax-equipped Silverado 1500 does things a bit differently. To activate the exhaust brake, which works by restricting airflow through the turbocharger via adjustable compressor vanes, the driver simply needs to initiate the Tow/Haul drive mode by pressing the button in the center of the drive mode selector dial. A message is then displayed in the instrument cluster indicating exhaust braking is active.

The diesel exhaust brake works in tandem with the truck’s grade braking system, which is also activated when in Tow/Haul. Grade braking has been available on Silverado since 2009 and saw its operating parameters expanded in 2013. The system functions by utilizing sensors on the vehicle (pitch, yaw, acceleration, deceleration, etc.) to know when the truck is on a grade and roughly how much weight is in tow.

In practice, we’ve found this system to work incredibly well—once it gets activated, anyway. When descending a grade, it takes a fair bit of use of the service brakes before the grade braking and exhaust brake launch into service. However, once they do, the truck does an incredible job of downshifting into the correct gear, often a lower one than the driver might feel is necessary (exhaust brakes are more efficient at higher rpm), and automatically modulating the exhaust brake to maintain whatever the last desired speed was. For example, if we were attempting to hold the truck at 55 mph with the service brakes, as soon as the engine braking kicked into action the truck would hold that same speed for the duration of the grade without needing to use them. We have been deeply impressed by how well this feature works, even at maximum combined weight and on grades as steep as eight percent.

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Plenty of Grunt but Not Quite Enough Power

Under the hood of our 2024 Silverado ZR2 is the company’s 3.0-liter turbodiesel inline-six Duramax. As the old saying goes, torque moves metal, and the Duramax offers a lot of it. The engine is rated at 495 lb-ft of twist, peaking at just 1,500 rpm. Even loaded to the max, our Duramax-powered Silverado ZR2 has never had an issue accelerating briskly from a stop. The truck’s 10-speed automatic transmission is eager to quickly drop gears to keep the engine in the meat of its torque curve. Climbing grades and maintaining speed has proved no issue, so long as the truck is able to begin climbing at the desired speed.

Trouble comes when momentum is broken. With only 305 hp on tap, which peaks at a high (for a diesel) 3,750 rpm, we’ve found that regaining lost speed and momentum at times proves challenging. It’s not an insurmountable issue, it just takes time. The transmission will drop gears, the engine will gain rpm, and eventually the truck gets back to the desired speed. Unfortunately, it’s often too little too late as traffic stacks up behind the trailer.

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Surprising Economy With Poor Range

One of the most impressive features of the 2024 Silverado 1500 ZR2 is its fuel economy and range when paired with the 3.0-liter Duramax diesel engine. Our yearlong review truck is EPA-rated at 20/22/21 mpg city/highway/combined and has routinely delivered better than 20 mpg in combined driving and nearly 500 miles of range on a tank. When running down the road with a trailer in tow that figure drops, but not quite as much as you’d think.

Over the course of 2,627 miles of towing we have observed an overall average economy of 12.6 mpg. The best tank averaged out to 14.02 mpg under ideal weather conditions on relatively flat roads. Our worst tank thus far hit right at 10.97 mpg and involved hilly terrain, two-lane roads, and a stiff headwind. We’ve noted that more than anything else, wind has the greatest impact on fuel economy. By comparison, our previous yearlong review rig, a 2022 Ford F-150 Raptor, would consistently return between 8 and 9 mpg while towing.

Despite its relatively decent towing economy, the Silverado ZR2 is hampered when it comes to range by its small, 24-gallon fuel tank. In theory, with the economy the Duramax engine is returning, we could go between 260 and 330 miles between fill-ups. However, the reality is that diesel stations aren’t always plentiful on long journeys to desolate places, and we’ve averaged just 202 miles per tank while towing.

This matters, because Ford’s smallest fuel tank for its 2024 F-150 crew cab is 30.6 gallons, and the company offers an optional 36-gallon unit. Ram offers a 26-gallon tank standard on its 2025 crew cab models, with the option to go to 33 gallons. By contrast, Chevy only offers the 24-gallon tank on all its Silverado 1500 pickups, with no option for more range.

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DEF Think Ahead

As light-duty diesel engine availability shrinks, so does familiarity with diesel exhaust fluid. Diesel exhaust fluid is a mix of automotive-grade urea and deionized water. The diesel exhaust fluid is injected into the exhaust system ahead of a catalyst to react with the NOx in the exhaust and convert it into less-harmful nitrogen and water. Chevy has fitted the 2024 Silverado with a 5.5-gallon tank for storing DEF, and it is supposed to last through an oil-change cycle of about 7,500 miles.

Towing, however, has proved to be incredibly consumptive when it comes to exhaust fluid. While under the most ideal circumstances the truck is said to consume about one gallon of DEF every 1,300 miles, but with a max-weight trailer in tow we are logging exhaust fluid range as low as 140 miles per gallon. That means a full tank will deplete in as few as 770 miles. The exhaust fluid story goes far deeper than just utilization rates, but that will need to wait for a future story.

For More On Our Long-Term 2024 Chevy Silverado ZR2:

• Is This The General’s Best Off-Roader? Long-Term 2024 Silverado ZR2 Arrival
• We Broke In Our Yearlong Review Silverado ZR2 By Driving It To The Bottom Of The Grand Canyon

• So Close To Perfection: 2024 Silverado ZR2 Interior Review