Filter clogging can have several causes. One of the main causes is bacteria build up due to condensation in the fuel system or tank.
In the last edition of the Auto Trade Journal, Finol Oils reports that bacteria is caused because differences in temperature caused by climate and in fuel systems, as in general, fuel systems are designed to return a significant portion of the fuel, not used for combustion, back to the tank.
The return fuel is very hot and when it comes into contact with the cooler fuel in the tank condensation is caused, which creates water on the inside of the tank, creating a habitat for bacteria to grow.
This bacteria than forms as sludge in your tank, this contaminant build up resulting from excessive microbial growth and bio-degradation of fuel can cause filter clogging. Micro-organisms, bacteria and enzyme activity, fungus, yeast and mould cause fuel degradation and the formation of waste products. The process is similar to milk turning into cottage cheese, a different form of milk.