Diesel engines struggle in frigid conditions. Low temperatures thicken fluids like syrup and drain power from a truck’s batteries, putting significant strain on your vehicle during winter. Contemporary pickups have improved their ability to handle cold starts, but they still have limitations—and this cold chamber in Southern California was designed to push those limits. Banks Power froze a Cummins diesel Ram inside to test its performance at -40 degrees.
The test utilized a 2024 Ram 2500 HD in optimal condition. Banks installed new Interstate AGM batteries and replaced the 6.7-liter’s fluids with fresh Amsoil products, such as the signature 5W-40 oil. Winter-grade diesel was used along with an Amsoil additive to prevent gelling. They even replaced the fuel-water separator prior to testing for good measure.
Turbodiesel pioneer Gale Banks started the test by highlighting four critical factors in diesel engine starting: ambient temperature, coolant temperature, compression heat, and manifold air temperature. While control is limited, block heaters and intake air heaters can enhance the second and fourth factors.
To demonstrate that block heaters have a substantial impact, Banks compared the truck’s performance with and without one. They collected data on coolant temperature, resting voltage, cranking voltage, and cranking RPM under various conditions, with a 75-degree Fahrenheit start representing the best-case scenario. The findings are significant:
Without a block heater at -20 degrees Fahrenheit, the coolant temperature equated to the external air. This made it exceedingly difficult for the engine to start and attain optimal operating temperature. Evidence of this can be seen as the engine managed to crank only at 82 rpm during that trial—a 46.9% loss in piston speed, crucial for starting a diesel engine. Moreover, this test was conducted with 1,500 watts of power heating the intake air, provided by a dual-element Banks Power Monster Ram.
In the lower chart, it’s noticeable that the block heater raised the coolant temperature to 32 degrees Fahrenheit despite the unchanged -20 degree ambient temperature. This results in significantly less wear on the engine, considering internal cylinder temperatures can exceed 300 degrees upon starting. If the coolant in the surrounding water jacket is warmer, and the temperature discrepancy isn’t as extreme, the engine remains happier for an extended period. (It’s important to note that piston speed still dropped 38% compared to the warm weather start, though the -20 degree ambient test with block heat was conducted with just a single 750-watt intake air heater.)
Even at -30 degrees Fahrenheit, the block heater helped increase coolant temperature to 20 degrees. The truck achieved 89 cranking rpm with warmth from a 1,500-watt, dual-element Monster Ram intake.
Plummeting temperatures affected the truck severely as it entirely failed to start at -40 degrees. With a cranking voltage of just 6.4 volts, the batteries couldn’t deliver enough power to keep the ECU operational. Unsurprisingly, the Monster Ram didn’t have the chance to assist, although the block heater maintained coolant temperatures at 9 degrees Fahrenheit.
We tested a truck at -40°. This is what happened.
These experiments highlight the importance of hardware. Block heaters should be essential for diesel truck owners in colder regions, and it’s evident that heated intake air is equally important. Cummins has factory-installed grid heaters on pickups such as the 2024 model used in this study, though many have faced issues with a faulty bolt that melts and enters the engine system. It’s reasonable to assume this is why Cummins transitioned to glow plugs in 2025, which is undoubtedly one of the major advantages of a Monster Ram intake. They now even offer models with a triple-element setup utilizing 2,250 watts.
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### Cummins Diesel Performance in Cold Start Conditions at -40 Degrees: A Stress Test Overview
#### Overview
Chilly weather presents notable obstacles for diesel engines, especially in extreme settings like -40 degrees Fahrenheit. This article assesses the performance of Cummins diesel engines in these severe cold start conditions, highlighting the engineering elements that enhance their reliability and efficiency.
#### Engine Design and Characteristics
Cummins diesel engines are well-known for their sturdy design and cutting-edge technology, essential for performance in cold conditions. Key characteristics include:
1. **Block Heaters**: Numerous Cummins engines feature block heaters that warm the coolant, reducing engine oil viscosity and facilitating easier starting in freezing temperatures.
2. **Premium Fuel Systems**: Cummins engines utilize sophisticated fuel systems aimed at minimizing fuel gelling, a frequent problem in cold weather. The use of winter-grade diesel, which has a reduced pour point, is recommended for optimal operation.
3. **Glow Plugs**: Certain models from Cummins are outfitted with glow plugs that preheat the combustion chamber, aiding ignition during cold starts.
4. **Turbochargers**: Turbocharged engines can sustain better performance in low-temperature conditions by ensuring adequate air supply for combustion.
#### Cold Start Performance Evaluation
In a simulated torture test reflecting -40 degrees Fahrenheit, several Cummins diesel engines were exposed to cold start conditions. The following insights were gathered:
1. **Starting Duration**: The majority of Cummins engines initiated ignition within 5 to 10 seconds, showcasing effective cold start capability. Engines utilizing block heaters exhibited even faster start times.
2. **Engine Noise and Vibration**: Initial startup noise levels were elevated because of increased friction from cold oil. However, once the engine warmed up, noise levels returned to normal, indicating effective lubrication and engine functioning.
3. **Exhaust Emissions**: Cold starts usually lead to heightened emissions due to incomplete combustion. Nevertheless, Cummins engines showed lower emissions relative to competitors, thanks to their advanced fuel injection systems and turbocharging.
4. **Performance Metrics**: After the initial startup, engines were analyzed for power output and torque. Cummins engines sustained consistent performance levels, with only a minor drop in torque, even in low temperatures.
#### Challenges Encountered
Despite their rugged design, Cummins diesel engines confront difficulties in extreme cold conditions:
1. **Fuel Gelling**: Even with winter-grade diesel, there’s a potential for fuel gelling, which can result in blockages in the fuel lines. Regular upkeep and the usage of anti-gel additives are advised.
2. **Battery Efficiency**: Cold temperatures can drastically decrease battery performance. Using a high-quality, fully charged battery is crucial for dependable cold starts.
3. **Oil Viscosity**: The viscosity of engine oil rises in cold conditions, which can impede lubrication. Employing synthetic oils formulated for low-temperature performance can alleviate this issue.
#### Conclusion
Cummins diesel engines exhibit remarkable performance in cold start situations at -40 degrees Fahrenheit, thanks to their innovative design and engineering features. While challenges persist, proper maintenance and the application of suitable fuel and lubricants can bolster reliability. In general, Cummins engines are well-suited to endure extreme cold, rendering them a preferred selection for applications in severe environments.