2027 Silverado’s Lower-Power V8 Tows 4,000 Pounds More on Regular Gas

The 2027 Chevrolet Silverado 1500’s engine specifications reverse the usual horsepower hierarchy. Its new 5.7-liter V8 produces 402 horsepower and 428 pound-feet of torque but can tow up to 13,700 pounds. The larger 6.6-liter makes 481 horsepower and 501 pound-feet, yet its maximum towing rating is 9,700 pounds. Maximum payload also drops from 2,170 pounds with the 5.7-liter to 1,510 pounds with the 6.6-liter.

GM has paired that higher-output 6.6-liter with a clean-sheet wet-sump lubrication system and an extensive validation program. More than 200 engines at different build stages have reportedly been undergoing laboratory tests, while development teams are working toward more than 2.4 million kilometers of road validation. The redesign and preproduction testing address durability and manufacturing quality, but long-term reliability will remain an open question until customer trucks accumulate substantial mileage across different climates and workloads.

Truck ratings depend on more than engine output

The specification gap does not mean the 5.7-liter is inherently stronger than the 6.6-liter. Towing and payload limits apply to complete vehicle configurations, rather than engines in isolation. Curb weight, trim equipment, suspension, tires, cooling capacity, axle configuration and other hardware can all determine the certified limit. GM has not isolated a single factor that accounts for the larger engine’s lower work ratings.

The practical consequence is nevertheless clear. In their highest-rated Silverado configurations, the 5.7-liter can tow 4,000 pounds more and carry 660 pounds more payload than the 6.6-liter. Horsepower describes the rate at which an engine can perform work; it does not, by itself, establish how much a complete truck is rated to pull or carry.

The same hierarchy appears in the mechanically related Sierra. GMC’s official 2027 Sierra specifications confirm that the 402-horsepower 5.7-liter can tow up to 13,500 pounds when properly equipped, while the 6.6-liter produces 481 horsepower and 501 pound-feet. The corresponding Sierra payload limits are 2,140 pounds for the 5.7-liter and 1,450 pounds for the 6.6-liter, and the 6.6-liter’s towing limit is 9,400 pounds. All four Sierra engines use a 10-speed automatic transmission, while a 34-gallon tank is available with the V8s.

The 6.6-liter gets a clean-sheet oiling system

The 6.6-liter retains a conventional wet sump rather than the dry-sump arrangement used in GM’s Corvette application, but the internal oiling architecture was comprehensively revised. Larger lifter galleries provide greater flow paths, and dual oil feeds serve the main bearings. GM also uses machined passages to improve manufacturing cleanliness instead of depending solely on as-cast internal surfaces.

An oil cooler is integrated into the oil-pan assembly. A continuously variable displacement pump changes its delivery according to operating demand, rather than continually pumping for the most severe load condition. Reducing unnecessary oil-pump work under lighter loads can limit parasitic losses, while greater delivery remains available as engine demands rise. Both new V8s use eight quarts of dexos1 full-synthetic SAE 0W-30 oil with the filter.

The larger engine’s output also reflects a 12.5:1 compression ratio, a larger throttle body, a redesigned intake and a fuel system combining direct and port injection. These features support higher output, but the compression ratio also puts fuel grade into the ownership equation.

More power brings a premium-fuel tradeoff

The Silverado and Sierra manuals recommend gasoline rated at 91 octane or higher for the 6.6-liter. Regular 87-octane fuel is permitted when premium is unavailable, but GM says using it will reduce performance and drivability. No separate horsepower figure has been published for operation on regular fuel, leaving the size of that reduction unresolved.

The 5.7-liter specifies regular 87-octane gasoline. For the 6.6-liter, the difference between regular and premium becomes a recurring operating expense, especially when filling a 34-gallon tank. The exact additional cost depends on local prices, but owners seeking the larger engine’s intended performance will have to account for that spread at each fill-up.

The 6.6-liter remains the output leader and serves specialized or high-end configurations, including the Silverado ZR2 and High Country and the Sierra AT4X and Denali. It is standard in the Sierra Denali Ultimate. For maximum published work ratings, however, the lower-power 5.7-liter is the consequential V8: it pulls and carries more in the highest-rated configurations while running on regular gasoline.

By Thomas Caldwell — AMI’s senior editor for mechanical and mobility engineering, covering vehicle electronics, systems integration, electrification, chassis systems, propulsion, and safety policy.