Do you really need a heavy-duty Diesel pickup truck when towing a lighter trailer (under about 7,000 lbs)? This is what we aim to find out in this Denver 100 MPG towing loop. The pickup trucks we have are: a 2025 GMC Sierra 1500 AT4X AEV Edition with a 3.0L Duramax turbo-diesel I6, and a 2025 Chevy Silverado HD 2500 Trail Boss with a 6.6L Duramax turbo-diesel V8. Which one will be more efficient and cost less after towing a trailer on the highway for 115 miles? Let’s find out!
This real-world test would not be possible with our friends at Weigh-Safe hitches and Complete Trailers. Thank you for the support.
Light-Duty Diesel
The GM 3.0L Duramax turbo-diesel is the only Diesel engine in its class. The latest LZ0 version of this engine is rated at 305 hp @ 3,750 rpm and 495 lb-ft of torque @ 2,750 rpm. This is impressive. This factory spec engine is producing over 100 horsepower per liter of displacement. This engine is mated to a 10-speed automatic transmission and a 3.42 to 1 rear axle ratio. This engine is being fed by a 24-gallon fuel tank.
Heavy-Duty Diesel
The 2025 Silverado HD is equipped with the latest L5P version of the 6.6L Duramax. It’s rated at 470 hp @ 2,800 rpm and 975 lb-ft of torque @ 1,600 rpm. It’s mated to a 10-speed Allison-branded automatic transmission and a 3.42 to 1 rear axle ratio. This engine is being fed by a 36-gallon fuel tank.
Denver 100 Loop
For this test we are pulling nearly identical InTech 24-foot enclosed trailers. The size and axles of these two trailers are identical, but one of the trailers has a couple more accessories (A/C unit on the roof). One of the trailers weighs about 400 lbs more than the other. One empty trailer weighs 4,000 lbs, the other one weighs 4,400 lbs.
After driving the same 115-mile loop at the same time, Kase and I go to the same fuel pump to get the final numbers.
The 3.0L Duramax registers 14.3 MPG at the pump. The big 6.6L Duramax registers 11.8 MPG. We conclude that when you are pulling trailers that weight up to about 7,000 lbs – the smaller half-ton full-size pickup truck works the best. As soon as, you start to tow much over 7,000 lbs – that’s when you want to consider the bigger HD pickup truck.
What do you think? Take a look at the video below.
