During the change over period from residual to distillate fuel the final fuel filters clog at a decreasing time interval. What is the most likely cause?

Correct Answer: Option D — Incompatibility of the fuels resulting in asphaltenes of the residual fuel precipitating out.

Blending incompatible residual and distillate fuels disrupts the chemical stability of the asphaltene suspension. The sudden solvency change causes heavy asphaltic compounds to precipitate rapidly, severely blinding and clogging final fuel filters.