Mechanically speaking, the light-duty 2020 Sierra diesel and 2020 Silverado diesel are mechanically identical. However, when it comes to fuel economy, the Silverado bests its Sierra counterpart by several MPG. Here’s why.
Before we dive into the explanation, let’s first examine why the MPG discrepancy actually matters. For starters, both full-size light-duty pickups ride on the same GM T1 vehicle platform, and both come equipped with the same 3.0L inline six-cylinder LM2 turbo-diesel Duramax engine.
The 2020 Sierra diesel and 2020 Silverado diesel also produce identical output figures of 277 horsepower at 3,750 RPM and 460 pound-feet of torque at 1,500 RPM. Both also utilize the same GM 10L80 10-speed automatic transmission.
So then, it would stand to reason that both trucks would return the same MPG numbers, right?
As it turns out, the 2020 Silverado diesel delivers higher fuel economy than the 2020 Sierra diesel. With the diesel engine option in 2WD selected for both trucks, the Sierra returns 30 MPG on the highway, 23 MPG in the city, and 26 MPG combined, which means the Sierra is down 3 MPG on the highway and 1 MPG combined compared to the Silvy. City MPG figures are identical between the two trucks.
So what gives? We reached out to Chevrolet Truck and Full-size SUV Communications manager Monte Doran, who explained the difference.
“Compared to Chevrolet, GMC models tend to have more content and are thus tested at a higher weight class than Chevrolet models,” Doran wrote. “Additionally, GMC’s high-volume models use more aggressive all-terrain tires compared to the all-season tires for Chevrolet high-volume models.”
GMC and Buick Communications Manager Stuart Fowle also chimed in, writing, “One additional difference is aerodynamics. Customers come to GMC seeking bold design tend [sic] to be less aerodynamic as a result.”
Despite the its lower MPG figures compared to the Silverado, the 2020 GMC Sierra diesel still posts fuel returns roughly on par with rivals from Ram and Ford.
We’ve broken down the figures for both the 2020 Sierra diesel, Silverado diesel, and its two biggest rivals below. Note that all figures correspond to 2WD model variants.
|Vehicle||Engine||Displacement||Configuration||Horsepower @ RPM||Torque @ RPM||MPG (hwy/city/combined)||MPG vs Sierra (hwy/city/combined)|
|2020 GMC Sierra 1500||Duramax Diesel LM2||3.0L||DOHC||277 @ 3750||460 @ 1500||30/23/26||-/-/-|
|2020 Chevrolet Silverado 1500||Duramax Diesel LM2||3.0L||DOHC||277 @ 3750||460 @ 1500||33/23/27||+3/-/+1|
|2020 Ram 1500||EcoDiesel||3.0L||DOHC||260 @ 3600||480 @ 1600||32/22/26||+2/-1/-|
|2020 Ford F-150||Power Stroke Diesel Lion||3.0L||DOHC||250 @ 3250||440 @ 1750||30/22/25||-/-1/-1|