REDMOND, Ore. — A powerful and refined diesel headlines new features on the 2020 Chevrolet Silverado 1500 pickup, as General Motors’ best-selling brand looks to change perceptions that its full-size pickup is an also-ran compared to Fiat Chrysler’s Ram models.

GM’s all-new straight-six diesel is smooth, amazingly quiet and likely to hit the market at least a couple of months ahead of Ram’s corresponding new 3.0-liter light-truck diesel V-6.

Diesels have fallen badly out of fashion with car buyers, but they still have devotees among pickup owners. That’s because diesels generate more torque — which matters most when towing — and use less fuel than comparable gasoline engines.

After years when they didn’t offer diesels in the light-duty 1500/150 trucks that account for around two-thirds of pickup sales, Chevy, Ford, GMC and Ram have made diesels the latest front in the Truck Wars. The GMC Sierra 1500’s diesel will be available shortly, using the same engine as Chevy.

The Silverado 1500 diesel should go on sale any day.

The only holdup is getting final EPA certification of the pickup’s fuel economy rating, a step that normally goes without saying but has been delayed for many new 2020-model vehicles because of the month-plus government shutdown last December and January.

Chevy’s already shipping diesels to dealers. The cost premium over the 5.3L V-8 is $2,495, the same bump as to get a 6.2L gasoline V8. It’s a considerably smaller premium than Ram charges for the old diesel V6 in the carryover Ram Classic pickup it continues to build.

A 10-speed automatic transmission is standard with Chevy’s diesel.

Diesels are expensive engines, because they have extra parts, including the emissions equipment Volkswagen left off its vehicles in the scandal that virtually killed the market for diesel cars.

GM’s new Duramax 3.0L is the first new inline six-cylinder engine the company has developed since a 4.2L model that powered midsize SUVs for a few years early this century.

Straight-sixes, as the engines are often called, are less prone to vibration than some other engines. That’s particularly useful for diesels, which tend to be louder and shake more than gasoline engines.

Luxury brands like straight-sixes for their silky-smooth operation. BMW has used them for years, and Mercedes and Jaguar Land Rover recently introduced new ones to replace V-6s.

Chevy’s new straight-six diesel produces 277 horsepower and 460 pound-feet of torque. That compares with 250 hp and 440 pound-feet for Ford’s 3.0L diesel V6 that’s already on sale; and 260 hp/480 pound-feet for the 2020 Ram 1500’s 3.0L V6 diesel. The 2020 Ram 1500 diesel is due to go on sale in the third quarter.

Chevy has horsepower for bragging rights, but the 2020 Ram carries the day when it comes to torque, and correspondingly in towing capacity, where it claims 12,560 pounds. I’d say that’s a ton more than Chevy’s 9,300 towing capacity, but at 3,260 pounds, it’s nearly a ton and a half. Ford’s diesel F-150 splits the difference with 11,400 pounds of towing capacity.

Built in Flint, Mich., the 3.0L Duramax diesel should eventually account for around 10% of total Silverado 1500 sales. Duramax is the brand name GM uses for its diesels.

Driving impressions

Even the most modern diesels are renowned for being louder, shakier and generally less refined that gasoline engines, but Chevy’s new I-6 changes that. It’s as smooth as a gasoline engine, and virtually devoid of the rattle that makes other diesels recognizable half a block away before you can read the badge on the tailgate.

The engine delivers 95% of its maximum torque at just 1,500 rpm. That means the brawny power you want when towing a heavy trailer is available quickly when you start, and on tap when you’re towing a trailer up a long hill or on a highway entrance ramp.

Without EPA-certified fuel economy figures, Chevy doesn’t have the mpg bragging point it undoubtedly hopes will offset Ford and Ram’s higher towing capacities, but the Silverado team ran some tests to simulate common driving situations on a spring day at the Indianapolis Motor Speedway.

Running at a steady 50 mph on the 2.5-mile oval track, Chevy claimed a 4WD diesel Silverado 1500 got 35.9 mpg, compared with 31.3 for a 4WD F-150 diesel. The gap narrowed to 1 mpg — 26.7 Chevy, 25.7 Ford — at 65 mph. The new Ram diesel wasn’t available to test.

If official EPA mpg ratings give the Silverado 1500 diesel anything like that advantage, fuel economy, power and quiet, smooth operation, this round of the Truck Wars could go to Chevrolet.