Is The Chevy 6.6 Diesel Any Good?

When you’re shopping for a Chevy Silverado HD, there are two engine options; the 6.6 V8 gas engine or the Duramax 6.6 turbo-diesel V8. A heavy-duty truck needs an engine that can keep up with any trailering and torque needs.

A Duramax 6.6L diesel engine is a great choice for a Chevy Silverado HD to maximize power and towing capabilities. A full-size heavy-duty pickup truck really benefits from this V-8 engine. It levels up a traditional diesel with a turbocharger that allows for more efficient power production.

The Duramax 6.6 turbo-diesel is an advanced engine with some incredible features. Understanding the details of the engine will help you make the right choice for your truck.

Overview

After its introduction in 2017, the new and improved turbo-diesel engine has remained in production for all the subsequent models. It is popular with Chevy Silverado owners, and can also be found in the GMC Sierra HD. The engine is a General Motors product, which owns both Chevy and GMC. The Duramax engine is the high-power choice for both lines of heavy-duty trucks.

The new 2017 design kept all of the best parts of a classic Duramax diesel engine while still making some crucial improvements. The reliable low-rpm torque you expect and need from a diesel engine is certainly a shining feature of this diesel. You can be confident pulling large loads with ease up steep hills and rocky terrain.

The Duramax 6.6 turbo-diesel is able to produce insane amounts of power with lower emissions and higher efficiency because of the variable-vane turbocharger on the cylinder heads. The temperature control from the variable-vane system allows the cylinders to be at lower pressure while still outputting increased power.

Lower pressure means the engine is able to function at higher efficiency, which will lower exhaust emissions and allow for higher functioning capabilities even on the steepest grades and roughest conditions. (source)

The engine is also kept cool from a new air intake system that uses a hood scoop to channel new cool air into the engine. Other improvements include a new rotating assembly, a tougher cylinder block, and a GM specialty control system. (source)

If you’re really putting your Silverado HD to the test and maxing out load weight, the engine may very well still get very hot. However, the Duramax turbo-diesel is equipped with an after-run cooling system.

The truck will automatically sense when the temperature of the engine is higher than it should be and encourage you to leave the engine running for a cool-down when you put it into park. If you turn off the truck, it can still restart itself to run the cooldown and then automatically shut off the truck when the engine has reached a good temperature.

Chevy’s 6.6 diesel has a higher towing capacity, improved acceleration, and greater ability to handle hills than any previous GM diesel engine. These features are improved further because it is paired with the new Allison 10-speed transmission. Chevy claims that the towing capacity of the engine is increased by 52% because of the 10-cylinder transmission. (source)

Specs

The Duramax 6.6 turbo-diesel V8 engine on a 2022 Chevy Silverado HD has 445 horsepower, 910 Lbs.-Ft. of torque, and a maximum towing weight of 36,000 pounds. (source)

Diesel vehicles are known for their high torque to low rpm ratio, and the Duramax is no different. The engine can put out 90% of peak torque (a little over 800 pound-feet) at just 1,550 rpm. It can also sustain this high torque all the way to 2,850 rpm. (source)

Diesel vs Gas

The 6.6 V8 gas engine is the other option for powering a Chevy Silverado HD. It comes with slightly lower specs for every category. Also based off of a 2022 Chevy Silverado HD, the gas engine has 401 horsepower, 464 Lbs.-Ft. of torque, and a maximum towing weight of 17.370 pounds.

The gas engine is paired with a 6-speed automatic transmission rather than the Allison 10-speed seen with the diesel. (source) This is still a powerful engine that will work great for a lot of people. However, when you’re looking at a heavy-duty truck it is likely that you may want a heavy-duty engine to match.

Diesel fuel costs more per gallon than gas, but diesel engines will provide better fuel efficiency, making it an economical choice. This is in part due to the heightened torque at low speeds. Torque is the rotational force from the engine that powers your truck forward. An engine that can very easily produce more of this type of power sees higher efficiency, meaning it uses less of its fuel to produce more power.

The torque is aided by the compression combustion system that diesel engines use. A gas engine will use ignition, but compression combustion is a more efficient use of fuel. Diesel engines also have a lower air-to-fuel ratio resulting in lower fuel consumption, meaning you don’t have to fill up as often. (source)

Traditional vs Turbocharger

The GM Duramax 6.6L diesel engine utilizes a turbocharger. This pumps fresh air and oxygen into the combustion chambers of the engine to increase the power of the engine. Since oxygen is needed to feed the combustion in the engine, the extra pumped in oxygen allows for a high-quality reaction in the combustion chambers, making the engine more efficient. 

Turbochargers are able to do this because they utilize the energy of the exhaust to turn a turbine as it is expelled from the engine. This exhaust turbine is connected to another intake turbine by a small axle.

As the exhaust leaves the engine forcefully, the forced turning of the exhaust turbine rotates the intake turbine which pumps fresh air forcefully into the intake. This allows for more oxygen present in the combustion chambers than a traditional intake.

At this point, logic would ask “if turbochargers give the engine more power, why doesn’t every car use one?” Well, turbochargers are typically used to improve fuel efficiency by giving increased power to a smaller engine.

In the case of the GM Duramax 6.6L diesel engine, however, no shortcuts were taken. With 8 firing cylinders, this engine comes with plenty of power already. The turbocharger was added to increase the power of the engine so that GM trucks using this engine are top quality and can handle heavy loads and rough roads with ease. (source)