For model year 2027, the L8T-replacing L8S is the standard engine in the heavy-duty Silverado and Sierra. Just like the 5.7- and 6.6-liter small blocks of the half-ton pickups, the heavy-duty workhorses with the heavy-duty gasser also drop the dipstick in favor of a sensor with a readout in the digital instrument cluster.
GM Trucks confirmed the switch first, and every trim gets it for model year 2027. Designated L8S in the order guide, the 6.6-liter small block develops a respectable 412 horsepower and 472 pound-feet (640 Newton-meters) of twist. Similar to the preceding L8T, said engine does not come with auto start-stop or dynamic fuel management in the form of cylinder deactivation.
Gifted with an iron block, the L8S differs from the L8T it replaces through an updated oiling system, a less restrictive air intake, a redesigned water pump, and a new oil cooler for good measure. Compared to its forerunner, it develops 11 more horsepower and 8 additional pound-feet.
When it comes to comparisons with the L76 and L78 engines of the half-ton Chevy Silverado and GMC Sierra, the L8S further differentiates itself through direct injection. Both half-ton truck engines feature dual injection, and the addition of port injection does come with a few advantages over a strictly direct setup. Not only does it eliminate carbon buildup on the intake valves, but it also enables a smoother idle and higher compression without knock.
The digital engine oil level readout may seem convenient, and it surely is. On the other hand, relying on a sensor to monitor engine oil levels isn’t as reliable in the long run as a physical dipstick under the hood. Leaving customers dependent on electronics and software for something this basic doesn’t sit right with me.
Photo: GM
Removing the dipstick feels cheap on the Detroit-based automaker’s part, even if the company saves very little money. Looking at the bigger picture, the sensor and digital readout are pricier to produce from the outset than a dipstick and its tube.
Beyond the L8S, prospective customers are further presented with an optional turbo diesel V8 advertised with 8.3 liters to its name. This Duramax is referred to as Mongoose or L6P, and it’s a clean-sheet design to boot. A different animal from the L5P it replaces, the 8.3 develops a massive 555 horsepower and 1,230 pound-feet (1,668 Newton-meters) of twist.
Because it’s lighter than the Duramax, the gasoline V8 is the better pick for payload. When properly equipped, the Tonawanda-produced engine is much obliged to handle 6,990 pounds (3,171 kilograms) compared to 6,170 (2,799) for the Duramax, which hails from Brookville, Ohio.
Towing, meanwhile, is the specialty of the segment’s largest diesel. For model year 2027, the Silverado HD with the L6P is good for up to 38,000 pounds (17,237 kilograms) compared to 19,000 (8,618) for the L8S.