New trucks usually carry the expectation of better technology and improved savings at the pump. The Fast Lane Truck tested this theory by pitting the new 2025 Ram 2500 against a 2021 model to see which one ruled the mpg chart. The outcome of their standard highway loop test was genuinely baffling for a team that has tested hundreds of pickups on the same stretch of Colorado pavement.
A Shift In Powertrain Strategy
Ram updated the 2025 model to chase better performance and refinement. The new truck uses a ZF eight-speed automatic and makes the High-Output Cummins engine standard across the lineup. This setup flows better air and hits harder with 430 horsepower compared to the old standard-output of 370 horsepower. Andre Smirnov noted that “the drivability and efficiency are kind of tied together because I think they nailed it.” The truck feels smoother than its predecessor because the transmission skips the low first gear for normal driving and utilizes a highway-friendly 3.42 axle ratio.
Why Every MPG Matters
Some drivers dismiss fuel economy in heavy trucks, but operating costs add up quickly when diesel is sitting around $3.59 a gallon. Andre explained his stance on efficiency by saying, “In my opinion, every little tiny bit matters, and that’s why I’m super psyched about this comparison.” The team ran both trucks on their standard 111-mile highway loop in identical 92-degree weather to get accurate mpg numbers. They used the manual top-off method at the same pump to eliminate any computer errors that might come from the digital trip meter.
The Shocking Pump Numbers
The expectation was for the new technology to edge out the old model. The 2021 Ram delivered a solid 21.3 miles per gallon. Andre called it a pretty great result for the older Cummins six-speed. The new truck needed to match that to justify the engineering updates and the $84,000 price tag. Instead, the 2025 High-Output model managed just 18.8 miles per gallon on the same loop. The gap was significant enough to leave the hosts scratching their heads. Andre admitted, “I am a little bit lost for words.”
Power Comes At A Cost
It appears that making the High-Output engine standard came with a penalty at the pump. The new 2025 Ram 2500 offers a better driving experience but burns more diesel to do it. Drivers looking for maximum range might actually miss the old standard-output configuration. Andre suggested, “You could argue that this engine with about 5,000 miles is not broken in yet.” The gap, however, seems too wide to close completely just with more miles.
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