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.
3.0L LM2 Duramax inline six-cylinder 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 |
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Comments
Yeah… a GMC is just a Chevy with “lock washers”.
Why does GM need to complicate everything.
Goal #1. Let’s make the most fuel efficient truck we can.
Goal #2. Let’s make the Sierra the biggest least fuel efficient Brick we can.
Wtf
It is highly conflicting. “Lets see how efficiently we can push a brick wall down the interstate.”
Sierra is still second most fuel efficient half-time on the market, only behind the Silverado.
Well no. Sierra 1500 Duramax 2wd is not outright second place. It’s one better city, two fewer highway, and equal combined compared to the 3rd generation Ram Ecodiesel in 2wd. I’d say it’s tied for second; not second. I mean there are only four total nameplates with an available e liter diesel, so the difference between 2nd and tying for second is a big difference.
I much prefer the straight six, and reviews seem to confirm so far that GM’s Italian engineers have produced a far more modern, simplified, responsive and overall superior power train than the two competitors, however, since GM refuses to pass along their saved cost products to their customers, it means little. What I mean is that the strides they made with respect to combining dpf and scr and co locating them in the engine bay using a less costly I6 architecture, manufacturong them in the U.S. instead of the UK or Italy, and utilizing less expensive solenoid injectors over piezo have little consequence if you’re offering the highest starting price of the three to let a customer drive a GM branded diesel.
There is little difference between a 5.6 ft and 6.5 ft bed in a pick-up truck. When are you going to build an extended cab with an 8 ft bed so the working man can use your truck?? You’re building for the fat 55 year old with shorts and sandals. deceiving yourselves because you are selling the toad truck into thinking it is what the American $ wants. Sure he buys a gaudy, glitzy, fat looking can’t-use-the-bed truck when there is no other choice sitting there on the new car lot to buy. If you offered a working man’s truck you would sell that too.