Your diesel filter water separator explained
Did you know that condensation in your diesel engine can get into your fuel system, contaminating your diesel? This is a less of a problem for petrol cars, as diesel engines (unlike petrol engines) don’t have vapor pressure to displace air. In other words, as the fuel tank heats up, the air expands and is forced out. Unfortunately, when the tank cools down, humid air is sucked back into the tank and water condenses on the cooler tank walls.