Risks of Diesel Fuel Contamination in 4WD's

Diesel fuel purchased in remote locations may be dirty and/or contaminated with water that fuel filters can clog up at any time, so carrying spare fuel filters on long expeditions is always a good idea.

Moreover, crossing deep-water obstacles without first allowing the differentials and transmission to cool down can cause water to be drawn into the diffs and transmission through their breathers when the air in them cools down and contracts. The best way to avoid this is to extend all breathers with rubber tubing to the engine compartment, but to a point that is high enough to prevent water entering the tubes. As a refinement, you may want to fit small in-line fuel filters to each breather tube to prevent dust being sucked into the diffs or transmission when these cool down.