What is the danger of using a fuel of bad quality?

Bad fuels most dangerous for the engine's fuel system. However, cylinder liner, piston rings, exhaust valves may also be affected. If first signs of using off-spec fuel are neglected severe damage may be a consequence.

1.Dangers for engine fuel system:
- Excessive wear, clogging or seizure of fuel injectors
- Excessive wear or seizure of fuel injection pump plunger and barrel
- Fuel injection pump may start leaking if diesel oil of too low viscosity used
- Chemical additive may attack fuel system packing, joints and seal causing various leakages

2.The danger for piston rings, pistons and liners.
Most common first sign of using bad quality fuel is engine cylinders exhaust temperatures rise above normal. In this case, an investigation to be carried out. The compression pressure to be checked and if it lower than the maker's recommendation, a thorough inspection through the scavenge space to be carried out to observe the piston rings condition. If broken piston rings found or liner surface condition is not satisfactory a subject cylinder unit must be overhauled at the earliest opportunity.
3.The danger to a turbocharger.
As the burning of an off-spec fuel often causes exhaust temperature rise this may lead to a turbocharged operation outside of designed parameters limits. Higher operational temperatures of the turbocharge lead to improper clearances in bearings, labyrinth seal and between rotating and stationary parts. At higher temperatures turbocharger parts material may loos it's base properties. All above factors may lead to a severe damage of the turbocharger.

Even if fuel test results obtained from the laboratory are satisfactory using of newly received fuel must be initiated with great care. Some tests are not included in standard testing procedure but if subject substances content exceeds limits this fuel may cause major failures.
Important fuel quality parameters outside of standard test scope (determined by the extended laboratory analyses):
- Catfines content must be as low or 0 - The fuel must be homogeneous. - The fuel must be stable
- Xylene content must be low or 0. Xylene equivalent leads to high risk of fuel pump problem. - Asphaltene content must be low or 0. Asphaltenes could also lead to the formation of carbon deposits in the piston grooves that could affect piston rings.
- Styrene content must below 20ppm
- DCPD content must below 20 ppm (GCMS Screening)
- Indene content must be below 100ppm (GCMS Screening)
- Fame content below 100

In case the fuel is unstable and with the presence of chemical contaminants at elevated levels, as well as the presence of high catfines in the supplied bunkers - this can be a contributing factor for piston ring breakage.

Preventive Actions:
Additional non-mandatory fuel analysis, which exceeds the ISO 8217:2005 standards, should be carried out if any of the below parameters are noted in the initial fuel analysis report. Such an advanced analysis will enable detection of organic acids, harmful chemicals and other contaminants.
- Catfines >50 ppm
- Sediment > 0.06% by mass
- Two out of the three being higher:
- - Calcium > 30
- - Phosphorus >15
- - Zinc > 15