How does my engine negatively affect fuel quality?

Written by Capt. Jeff Werner

A diesel engine uses only some of the fuel it pulls from the tank. All of that fuel goes to the high pressure fuel pump and to the injectors operating under enormous pressure and high temperatures.

The surplus fuel the engine is not using goes back to the tank. The fuel is continuously re-circulated and exposed to extreme pressure and heat, which results in the agglomeration of asphaltenes, the high carbon content and heavy fuel molecules. It leads to the formation of larger and larger clusters of solids, which are very difficult to completely combust. These solids may grow so large that they will not pass through the filter element and become part of the polymer and sludge build up clogging the filter.

In addition, hot fuel coming back to the tank will raise the fuel temperature in the tank, cause condensation and contribute to microbial contamination, fuel breakdown, bio-fouling and the build up of sludge and acid.

Large fuel droplets and high asphaltene concentrations require more time, more energy and higher temperatures to combust than is available in engines during the combustion cycle and before the exhaust valve opens.

Any device in the fuel system exposing fuel to heat and pressure, such as pumps, heaters, or centrifuges will increase the formation of asphaltenes and negatively impact combustion.

Capt. Jeff Werner, a Licensed USCG Master, has sailed professionally throughout the world. ┬áHe is also the Diesel Doctor, helping to keep your boat’s fuel clean and bright.

If you have additional questions for Capt. Jeff Werner, please email him