Chevy Silverado’s Duramax Diesel Late, Pricey

Long overdue, the Chevrolet Silverado and GMC Sierra fullsize pickup trucks will offer later this year for the first time a light-duty diesel engine that will carry a $3,890 premium over the Silverado’s 2.7L turbocharged gasoline 4-cyl. and a $2,495 premium over the 5.3L small-block gasoline V-8.

The all-aluminum Duramax 3.0L inline 6-cyl. diesel is priced identical to the Silverado’s current flagship powertrain, the redesigned 6.2L gasoline V-8 that won a Wards 10 Best Engines trophy this year and employs Dynamic Fuel Management, a sophisticated 17-mode cylinder-deactivation system.

With less than half the displacement, the light-duty Duramax delivers the same 460 lb.-ft. (624 Nm) of torque as the 6.2L V-8, but achieves that peak at 1,250 rpm – much earlier than the gasoline V-8 (which needs 4,100 rpm for peak torque).

As expected, the V-8 trounces the diesel’s 277 hp with a stout 420 hp. But the Duramax diesel’s key attribute is expected to be its real-world fuel economy.

EPA ratings are not yet available, and media test drives of the new engine occur later this month in Oregon. For reference, Ford touts a class-leading 30 mpg (7.8 L/100 km) highway rating for its 2-wheel-drive F-150 pickup.

As with other diesels, the EPA has been slow to certify the Duramax engine for sale in the U.S. 

The agency has been overly cautious in evaluating diesel engines for certification in the wake of Volkswagen’s underhanded rigging of diesel engines to treat nitrogen-oxide emissions only during government testing.

That means VW customers were logging millions of miles in diesel vehicles without proper emissions controls, resulting in unchecked pollution. VW and certain executives have faced fines and criminal charges following the 2015 scandal.

Chevy announced in May 2018 the ’19 Silverado 1500 would be available with the new 3.0L Duramax “in early 2019.” Speaking Wednesday to Wall Street analysts, General Motors President Mark Reuss calls for patience.

“Our 3.0L diesel is coming here shortly after we get certification from the EPA, which we have been waiting on but it's all ready to go,” Reuss says.

Not only is GM late to market with the engine, it’s the last to the fullsize market among the Detroit Three automakers, who dominate the pickup segment.

The three automakers were prepared more than a decade ago to launch light-duty diesels for fullsize pickups, but those plans were shelved for a variety of reasons. GM has offered a 4-cyl. diesel in its midsize pickups for the past three years.

FCA US was the first automaker to deliver a European-sourced 3.0L EcoDiesel in 2014, when the powerplant went on to win three consecutive Wards 10 Best Engines trophies. But the engine was pulled from the market in 2017 when enhanced testing by EPA and the California Air Resources Board cited FCA for emissions violations.

Last month, FCA settled a lawsuit with Ram and Jeep diesel owners to compensate them (up to $3,075 per owner) for repairs to bring their vehicles into emissions compliance. FCA officials have said a 3.0L EcoDiesel will be available in the ’19 Ram 1500 sometime this year and in the midsize Jeep Gladiator next year.

Ford introduced the 3.0L Power Stroke diesel V-6 last year in the F-150 pickup, and it earned a 2019 Wards 10 Best Engines trophy in its first year of eligibility. Wards Intelligence data shows 4.4% of F-150 buyers in MY ’18 chose the diesel.

For Chevrolet and GMC, the new 3.0L Duramax (pictured below), assembled in Flint, MI, represents GM’s first inline 6-cyl. light-duty truck diesel.

Starting in 1978, the two brands offered a version of Oldsmobile’s ill-fated 5.7L diesel V-8 in Class 1 Chevy C10 and GMC C1500 2-wheel-drive pickups. Notorious for being smoky, loud and unreliable, the GM engine helped make diesels a non-starter among consumers at the time.

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The 3.0L diesel, paired with GM’s 10-speed automatic transmission, will be available on LT, RST, LTZ and High Country models from Chevrolet.

The Duramax diesel incorporates driver-selectable stop/start technology; ceramic glow plugs for faster heating up; low-pressure exhaust-gas recirculation; a variable-geometry liquid-cooled turbocharger; a variable-pressure lubrication system; and an electronically variable intake manifold to optimize performance at all engine speeds.

The rotating assembly consists of a forged steel crankshaft, forged steel connecting rods and hypereutectic aluminum pistons. Thick piston crowns and reinforced top rings add strength to counteract high cylinder pressures enabled by turbocharging and the 15.0:1 compression ratio.

GM says a water-to-air intercooling system produces a cooler high-density air charge for greater power. Maximum boost pressure is 43.5 psi (3 bar).

The 36,250-psi (2,500-bar) common-rail fueling system uses solenoid-activated injectors with nine-hole nozzles for precise metering of the fuel for smooth idle and low combustion noise.

The energy density of diesel fuel is about 15% greater than that of gasoline, which is one reason why a diesel engine delivers more torque and better fuel efficiency than a gasoline engine of the same displacement.

That additional torque is readily available at lower engine speeds (relative to a gasoline engine), which makes diesel the proven choice for anyone who has something to tow.

Tow ratings for GM’s new 3.0L DOHC Duramax are not yet available, but the automaker says those specs will be released during test drives later this month.