Fuel Mileage On 2025 Duramax. Since my 2021 duramax got a new ecm flash from the dealer, it’s getting even better fuel mileage mid 20mpg canadian driven at the speed limit. The 2025 silverado duramax acted as a tow rig for us this week, and actually ended up being quite enjoyable to rack up some miles on.
It’s one hell of a powerhouse, making 305 horsepower but 495. I looking to purchase a new 3 liter.
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