Banks Power cold start Cummins testDiesel engines hate cold weather. Negative temperatures cause fluids to thicken like molasses while zapping power from a truck's batteries, making it awfully hard on your rig in the winter. Modern pickups have gotten pretty good at overcoming cold starts, but still, they have their limits—and this cold chamber in Southern California was built to exceed them. Banks Power froze a Cummins diesel Ram inside it to see how the pickup performs at -40 degrees.The experiment was conducted with a 2024 Ram 2500 HD in peak condition. Banks put new Interstate AGM batteries under the hood and swapped the 6.7-liter's fluids for fresh Amsoil products, like the brand's Signature Series 5W-40 oil. Winter diesel was used in combination with an Amsoil additive to prevent gelling, too. They even made sure to replace the fuel-water separator before testing for good measure.That's at the Thermal Dynamics lab in SoCal. Banks PowerTurbodiesel godfather Gale Banks introduced the test by listing four major factors in diesel engine start procedures: ambient temperature, coolant temperature, heat of compression, and manifold air temperature. You can only control so much, but thanks to block heaters and intake air heaters, you can augment the second and fourth factors.AdvertisementAdvertisementTo prove that block heaters make a massive difference, Banks tested the truck with and without one. They measured coolant temp, resting voltage, cranking voltage, and cranking RPM in various conditions, with a 75-degree Fahrenheit start acting as the best-case scenario. The results are telling:Banks PowerWithout a block heater at -20 degrees Fahrenheit, the coolant temperature matches the outside air. That makes it far harder for the engine to start and reach optimal operating temperature. You can see evidence of that as the engine could only crank at 82 rpm during that test—a 46.9% loss in piston speed, which a diesel engine depends on to start. And keep in mind that this test was performed with 1,500 watts of power warming the intake air, supplied by a dual-element Banks Power Monster Ram.If you look at the bottom chart, you'll notice that the block heater warmed the coolant temperature to 32 degrees Fahrenheit despite the same -20 degree ambient temp. This results in significantly less wear on an engine, given that internal cylinder temps can exceed 300 degrees on startup. If the coolant in the water jacket surrounding the cylinder is warmer, and the temperature difference isn't so great, then you have a happier engine for longer. (It's worth noting that the piston speed still dropped 38% compared to the warm weather start, though the -20 degree ambient temperature test with block heat was performed with only a single 750-watt intake air heater element.)Dual pre-heating cycles helped increase manifold air temp significantly. Banks PowerEven at -30 degrees Fahrenheit, the block heater helped boost coolant temperature to 20 degrees. The truck also achieved 89 cranking rpm with heat from a 1,500-watt, dual-element Monster Ram intake.AdvertisementAdvertisementTumbling temps took a toll on the truck as it completely failed to start at -40 degrees. With a cranking voltage of just 6.4 volts, the batteries couldn't provide the juice necessary to keep the ECU awake. Needless to say, the Monster Ram didn't get the opportunity to help, though the block heater kept coolant temps at 9 degrees Fahrenheit.These tests show why hardware matters so much. Block heaters should be a no-brainer for diesel truck owners in cold-weather states, and clearly, heated intake air matters as well. Cummins installed factory grid heaters on pickups like the 2024 model used in this test, though many have suffered from a faulty bolt that melts and finds its way into the engine. You have to assume that's why Cummins switched to glow plugs in 2025, and that's absolutely one of the biggest perks of a Monster Ram intake. Now, they even sell one with a triple-element setup utilizing 2,250 watts.Got a tip or question for the author? Contact them directly: caleb@thedrive.com
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