I bought a coolant filter mount and it came with a new Fleetguard WF2074 filter. Unfortunately, it has DCA4 additive for a 36 gallon cooling system so I can't use it. I've always wondered what these looked like inside, so here it is cut open. It's a paper element that seems to be stained by whatever the additive is inside. The additive seeped out. Coil spring. I removed the bottom plug in the element, and the center of the filter is packed full of additive. All the additive dumped out. Not sure if this is a date code, would be interesting to know how long this filter has been sitting around. I didn't expect to see that much additive inside the filter. If someone installed this filter on a typical 3 to 4 gallon cooling system I have a feeling it wouldn't end well.