The coolant filter should be changed out several time within the first year of having the 5.9 Cummins coolant filtration kit installed. The first filter should be changed out within the first 500 miles as it will catch the most debris. The second filter should be changed out at about 3000 miles. The third filter should be changed out after the first year. The intervals may vary depending on the amount of debris in the engine. We recommend cutting open the filters to determine how many times and how often the filter should be changed in the first year. If the filter is still very dirty after the second interval, you may want to do an additional filter change in between the 3000 mile mark and the end of the year. After the initial year, you should change the filter out once every year after that.