Modern turbo-diesel engines are remarkably powerful and efficient. Is it enough to make financial sense while towing a trailer? We take two new Ram HD trucks (one with a Cummins turbo-diesel and another with a HEMI V8) and compare them on the Denver 100 MPG loop while towing two identical trailers. Is it still cheaper to fill up a diesel truck when towing a trailer? Let’s dig in!
This video would not be possible without our friends at Weigh Safe Hitches, Complete Trailers, and Johnson Auto Plaza. Also, a huge thanks to the TFL video and logistics team (Ian, Cole, and Zach).
Both of these trucks have over 1,000 miles on their odometers. They are broken in. This Denver 100 MPG loop takes us about 123 miles. It’s a highway test with an average speed of around 60 MPH from start to finish.
The gasoline truck is a 2026 Ram HD 2500 Warlock with a 6.4L HEMI V8 that is rated at 405 hp and 429 lb-ft of torque. It’s mated to a ZF 8-speed automatic transmission and a 3.73-to-1 rear axle ratio.
The diesel truck is a 2025 Ram HD 2500 Big Horn with a 6.7L Cummins I6 turbo-diesel that is rated at 430 hp and 1,075 lb-ft of torque. It also uses an 8-speed ZF automatic transmission and it’s sending the power to a 3.42-to-1 rear axle ratio. This high-output diesel engine is the only version available for the new 2025+ pickup trucks. It adds $12,995 to the price of a new Ram HD.
The diesel engine is more powerful, more efficient, but it also makes the truck weigh around 1,100 lbs more than the HEMI-powered counterpart.
We are pulling 24-foot box car hauler trailers. They are nearly identical and weigh approximately 4,000 lbs each. These trailers are very tall and long, so they present a significant aerodynamic load on both trucks.
In the end, the HEMI V8 used 11.1 gallons of regular unleaded, returned 11.1 MPG, and cost $49.52 to fill up. The Cummins diesel used 9.3 gallons, returned 13.2 MPG, and cost $47.45 to fill up.
The diesel truck is 18.9% more efficient while pulling the same trailer on the same route. The diesel fuel was 14.4% more expensive for this test.
Given how the cost breaks down – it means one would have to drive approximately 639,000 miles with these fuel prices in order to pay off the $12,995 additional cost of the diesel engine. Naturally, the diesel truck also has an additional cost of the DEF, maintenance, and potential repairs.
In the end, the Cummins-powered Ram HD felt more stable and confident while towing these trailers in cross winds. The diesel-powered truck is also superior when towing over mountainous terrain (it does have an exhaust brake). However, if you don’t drive a lot of miles and if you do not regularly tow a trailer – the gasoline engine is simply a much better deal.
As a side note, the price of diesel fuel increased from a national average of $3.557 to $5.464 over one year. This is a staggering 56.3% year-over-year increase.
Please join the video below and let me know what you think.
