Originally Featured in Fleet Equipment Magazine:
Over time, cholesterol builds up in the veins of the human body, limiting blood flow and causing myriad other problems. Often known as the silent killer, cholesterol in the body is very similar to stiction in a diesel engine—the sticky-friction created from the build up of burnt hydrocarbons (oil or fuel). It is often the cause of “headache trucks” that never seem to perform well and are in the garage for frequent repairs.
Symptoms of stiction:
- Failed injector diagnosis;
- Hard starts;
- Rough idling;
- Poor acceleration; and
- Excessive black smoke;
Why stiction occurs
To increase the efficiency in modern diesel engines, manufacturers have increased the pressure at the tip of the injector. This increase provides for a better, more efficient burn with added power. Older injectors would put out 1,200 PSI at the injector tip but the new diesel engines put out 30,000 PSI. To achieve this increase in pressure, the manufacturers had to tighten the tolerance inside the injector, which increased the friction and temperature. The higher temperatures have a burning effect on the engine oil. A layer of oxidized oil forms slowing the injector’s performance and causing rough idle, poor acceleration, excessive black smoke and hard starts. As stiction builds, it can cause the injector to fail.
The spread of stiction
Originally, the stiction problem was thought to be limited to oil-fired injectors. However further testing has shown that stiction impairs the performance of the turbo, rings and the oil pump, too. Stiction is not limited to the oil-side of the diesel either. Oil and fuel are both hydrocarbons. When any hydrocarbon is over-heated, it leaves a sticky residue that can cause stiction, which can negatively impact the fuel system and transmission.
While not intentional in design, burnt hydrocarbons creating stiction are a natural byproduct of the diesel engine. Whether using synthetic oil or high quality fuel, stiction is inevitable.
Using a lubricant alone to prevent stiction is a temporary fix and does not ultimately solve the problem. Stiction can be removed from the oil or fuel system via the application of an appropriate additive such as Hot Shot’s Secret Stiction Eliminator that includes detergents and dispersants specifically designed to treat stiction.
By Chris Gabrelcik, president and chief executive officer of Lubrication Specialties Inc.