Chevy’s 2027 half-ton diesel trucks get 34-gallon tanks but lose under-seat storage

General Motors is giving its redesigned 2027 Chevrolet Silverado 1500 and GMC Sierra 1500 a 34-gallon extended-range fuel tank, and the diesel versions pair it with a much larger exhaust-fluid reservoir. Autoblog reported on November 3 that the space came from deleting the rear under-seat storage bins. Range goes up and a convenient hiding place goes away.

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The trade centers on the 3.0-liter Duramax inline-six, the only diesel in the half-ton lineup. Owners who tow or cover long highway stretches get fewer fuel stops, while those who kept tools, documents or a laptop under the back seat must find another spot. GM has not published a capacity for the new diesel exhaust fluid tank, so the full scale of the repackaging is still unclear.

A 34-gallon tank and the 900-mile Duramax

Autoblog’s Roy Robles wrote that the 34-gallon extended-range tank is arriving across the half-ton lineup and that it pairs with the bigger exhaust-fluid tank on diesel trucks. For context, GM Authority reported in August that 2026 Silverados and Sierras carry between 22 and 28 gallons depending on cab, bed and engine, with no larger tank offered at all. The same outlet said the extended-range tank is optional with the Duramax diesel and the 5.7-liter V8, standard with the 6.6-liter V8, and unavailable with the 2.7-liter TurboMax four-cylinder, as detailed in its report on the fuel option.

The numbers add up to a long leash. The Drive calculated that a 2027 Silverado with the 3.0-liter Duramax can go more than 900 miles on one tank, noting that GM estimates 27 mpg on the highway for a two-wheel-drive truck while the author reported 30 mpg in real-world driving. Those mileage figures come from a Sept. 17 piece by Caleb Jacobs, which also described 34 gallons as the larger tank available on both trucks.

Diesel exhaust fluid, the urea solution that modern diesels inject into the exhaust to cut nitrogen oxide emissions, has to be topped up periodically, and a bigger reservoir stretches the interval between refills. Pairing it with a larger fuel tank means a long-distance driver could, in principle, run both low at similar intervals rather than stopping for one or the other. The Drive noted that GM’s own materials mention revised DEF level indicators for the 2027 trucks, a sign that the dashboard readouts were reworked alongside the hardware. For a truck that can cover 900 miles on a tank, a clear fluid gauge matters as much as the fuel gauge, because an empty reservoir can limit the engine.

Rear storage bins traded for tank and exhaust-fluid space

Robles attributes the storage loss to GM Authority, which said the extra fuel capacity sits beneath the floorboards, and he concludes that GM removed the rear under-seat bins to make room for the bigger diesel exhaust fluid tank and the 34-gallon fuel tank. He calls the sacrifice a perfectly acceptable trade-off for serious truck owners, arguing that range and towing matter more to Duramax buyers than a hidden bin. He also points to remaining places for small items: the redesigned front center console, the standard gloveboxes and lockable aftermarket bed boxes.

Earlier reporting hinted at the cut. In August, GM Authority studied the online visualizer for the new truck and found rear seatbacks without the split-back cushions that house hidden compartments introduced on the Silverado for the 2019 model year. At that point GM had not confirmed anything, and the outlet cautioned that preliminary imagery can change before dealers receive trucks.

Those compartments are not available on every trim today. They sit in an up-level rear seat package on the LT, RST and Trail Boss when ordered with leather, are standard on the ZR2, LTZ and High Country, and have never been offered on the Work Truck or Custom. The loss therefore lands hardest on higher-priced crew cabs whose owners paid for the feature.

Redesign timing, V8 changes and the missing GM confirmation

Chevrolet unveiled the 2027 Silverado 1500 on June 16, according to Jalopnik’s reveal coverage, with a 2.7-liter turbo four, the Duramax diesel and two new naturally aspirated V8s of 5.7 and 6.6 liters. Executive chief engineer Mark Dickens said the engines underwent extensive testing to make sure they deliver the durability, capability and dependability Silverado customers expect. Pricing and an on-sale date were not announced at the time.

Trade reporting added that the Duramax is now available on the Work Truck trim for the first time, a detail covered by Automotive Fleet, which also noted that Chevrolet had not released power, torque, towing or payload ratings. Autoblog adds that the redesigned trucks offer less cabin volume than the 2026 models, citing an earlier report, so the storage question is part of a broader squeeze on interior space.

The open item is documentation. Neither GM nor Chevrolet has published the size of the diesel exhaust fluid tank or a build sheet that confirms exactly which bins disappear, and the claim rests on Autoblog’s reading of GM Authority. Dealer order guides, which typically circulate ahead of deliveries expected in late 2026, would be the first place a definitive answer appears.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

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