Duramax vs 6.2L EcoTec3: Diesel or Gas Silverado?

The 3.0L Duramax diesel option in the T1XX Silverado has made the diesel-vs-gas question real for half-ton buyers for the first time. Previously it was academic — the Duramax was only in heavy-duty trucks. Now you can actually cross-shop the 3.0L I-6 diesel against the 6.2L EcoTec3 V8. Here’s the honest answer.

The 3.0L Duramax: What It Is

The 3.0L Duramax LM2 is a turbocharged inline-6 diesel producing 277 hp and 460 lb-ft of torque (2020+ specs). It’s paired exclusively with the 10-speed Hydra-Matic 10L80E. EPA fuel economy ratings: 23 city / 33 highway / 26 combined for 2WD — making it one of the most fuel-efficient full-size trucks available. Maximum tow rating: 9,300 lbs in properly equipped configuration.

The 6.2L EcoTec3: What It Is

The 6.2L L87 naturally-aspirated V8 produces 420 hp and 460 lb-ft of torque — exactly the same torque as the diesel but with 143 more horsepower and a completely different character. Paired with the 10-speed 10L80E. EPA ratings: 15 city / 20 highway / 17 combined for 2WD (4WD: 14/19). Maximum tow rating: 13,400 lbs with Max Trailering Package. See: 5.3L vs 6.2L comparison.

Fuel Cost Over 100,000 Miles

The diesel’s fuel economy advantage is real — roughly 9 MPG better highway. At 15,000 miles/year and current fuel prices (assuming diesel ~$0.30/gallon premium over regular unleaded): the Duramax saves approximately 125 gallons per year = $475/year at $3.80/gallon gas and $4.10 diesel. Over 100,000 miles at that rate: approximately $3,000 in fuel savings. The diesel commands a $2,500–4,500 new-truck price premium. The fuel savings roughly break even over the truck’s life — which means the decision should be made on criteria other than fuel savings alone.

All of that assumes EPA-rated economy. If you already own one, run your last few tanks through the Fuel Mileage Calculator first — the payback math only holds if your real number matches the sticker.

Towing: Where the 6.2L Wins

The 6.2L tows 13,400 lbs to the diesel’s 9,300 lbs — 44% more maximum capacity. For buyers regularly towing above 9,000 lbs, this isn’t a close call. The 6.2L also maintains speed on grades better under heavy loads (more horsepower reserve), runs cooler under sustained high-load towing, and has simpler emissions hardware. If towing is primary use, the 6.2L is the correct engine.

Fuel Economy: Where the Diesel Wins

For highway drivers who rarely tow but rack up miles, the diesel’s 33 MPG highway vs the 6.2L’s 20 MPG is significant. A 50,000 miles/year highway driver saves 650+ gallons annually — over $2,400/year at current prices. The economics flip entirely in favor of the diesel at high mileage. Fleet buyers and long-haul drivers who rarely tow heavy loads make a legitimate case for the diesel.

Maintenance Cost: The Diesel Penalty

Diesel maintenance is more expensive than gasoline: diesel oil changes cost more (more capacity, specialized oil), DEF (Diesel Exhaust Fluid) requires regular top-off ($15–30/gallon, ~1 gallon per 2,500 miles), and the emissions system (DPF, SCR, EGR) requires periodic maintenance and eventual replacement ($2,000–4,000 when components fail). A diesel fuel filter change is more involved than a gasoline equivalent. Over 150,000 miles, diesel maintenance typically costs $3,000–6,000 more than an equivalent gasoline engine.

Reliability: Early Track Record

The 3.0L Duramax is a relatively new engine in the half-ton application (introduced 2019). Early owner reports are generally positive but the long-term track record doesn’t exist yet — there are no 200,000-mile 3.0L Duramax Silverados to study yet. The 6.2L EcoTec3’s architecture is derived from the proven LS family with decades of high-mileage data. For buyers who keep trucks past 150,000 miles, the 6.2L’s longer proven reliability track record is a real advantage.

The Verdict

Buy the 3.0L Duramax if: You drive 20,000+ miles/year primarily on the highway, rarely tow above 8,000 lbs, plan to keep the truck 10+ years and want the best fuel efficiency, or the emissions-compliant diesel operation is important for your use case (fleet, commercial).

Buy the 6.2L EcoTec3 if: You regularly tow above 9,000 lbs, want a proven high-mileage powertrain, prioritize horsepower and performance feel, want lower maintenance complexity, or are keeping the truck under 10 years. The 6.2L is also simply a more enjoyable engine — 420 hp delivers a driving experience the diesel can’t match.

The honest take: For most half-ton buyers who tow occasionally and drive moderate miles, the 6.2L is the better all-around choice. The diesel makes a compelling case only for specific high-mileage or fleet use cases where the fuel savings math actually works out.

For T1XX platform info: T1XX complete guide. For towing capacity by year: Silverado towing capacity guide.

Keep going: find every K2XX guide, known problem and fix in the K2XX Hub and the T1XX Hub.

Find every repair, buying, maintenance, and troubleshooting guide in the K2XX Owner’s Hub.