2025 Chevy 6.6 Duramax Mpg. 2025 chevy 6.6 duramax mpg.  — the truck's l5p duramax diesel engine received a substantial bump in power and torque thanks to a stout list of upgrades, including a new turbocharger, improved piston design, enhancements to the.

Here’s the average duramax diesel mpg you can expect for popular trucks  — factory fill is delvac 15w40.