The problem is simple: the stock Duramax oil pan does not drain from the true low point. A weld nut protrudes into the sump, leaving a pool of dirty oil behind every time you service the engine. Because the pickup tube sits submerged in that trapped oil, contaminated oil also stays inside the tube. That means an oil change is never fully clean. Old oil and debris remain in the pan and pickup, then mix right back into the fresh fill. Our Banks CoolRunner Oil Pan fixes the drain path. The magnetic drain plug is placed at the lowest point, so the sump drains completely. Once the trapped oil is gone, the pickup tube is no longer submerged and it drains too. On top of that, the CoolRunner cools better than stock and other aftermarket oil pans, so you get cleaner oil changes and better oil control from the same upgrade.
The video argues that the stock engine oil pan traps a significant amount of used oil even after a normal oil change. According to the demonstration, roughly a quart of dirty oil remains in the sump because the drain opening is not positioned at the true lowest point of the pan.
The drain plug's weld nut protrudes approximately 3/4 inch into the pan, creating a standpipe effect that leaves a layer of oil behind after draining.
The trapped oil affects more than the bottom of the sump. The pickup tube remains submerged below the retained oil level, preventing air from entering and allowing the oil inside the tube to drain.
As a result, used oil remains both in the pan and inside the pickup passage after a conventional oil change.
To make the problem visible, the presenters use a clear plastic oil pan designed to duplicate the geometry of the factory pan. The transparent construction reveals the pickup tube, mid pan, and drain area.
The engine is filled to the proper oil level, operated, and then drained so the amount and location of the remaining oil can be observed directly.
After draining stops, oil remains below the level established by the inward-protruding weld nut. Because the remaining oil is deep enough to keep the pickup submerged, oil also remains trapped inside the pickup tube.
According to the demonstration, approximately a quart of used oil can remain in the system after a normal drain.
The practical concern is that this residual oil mixes with the fresh oil added during every service. Instead of replacing the entire volume in the sump and pickup, each oil change leaves some of the previous oil behind.
The video presents more complete evacuation of the used oil as preferable for maintaining cleaner engine oil between service intervals.
The Banks CoolRunner oil pan addresses the problem by positioning its magnetic drain plug at the lowest point of the sump.
Without the raised obstruction found in the factory arrangement, oil can continue flowing toward the drain until the bottom of the pan is effectively emptied.
Completely draining the sump also allows the oil level to fall below the pickup tube inlet. Once the pickup is exposed to air, the oil remaining inside the tube can drain into the pan and exit through the drain opening.
Banks therefore presents the CoolRunner design as addressing both sources of residual oil: the oil retained in the sump and the oil trapped inside the pickup tube.
In addition to improved drainage, Banks states that the CoolRunner provides better oil cooling than the stock pan and other aftermarket oil pans.
The excerpt does not provide supporting temperature measurements or detailed cooling-test results, so the primary demonstrated benefit in this segment is the CoolRunner's complete-drain design and low-mounted magnetic drain plug.
