“What’s the service interval on my DEF Filter?” This is a common question we’ve been getting in our region lately. Many mechanics we hear from weren’t even aware there was a DEF Fluid filter. For one reason or another, there hasn’t been a lot of education around the serviceable DEF Fluid Filter. Where is the filter located? Inside the doser pump (Bosch calls it a DEF Supply Module.) Once located on the vehicle, the filter is easy to service. Simply remove the filter cap, use the extraction tool (if provided) to remove the existing filter. Slip the replacement filter in place and reinstall the cap.
How often should the filter be replaced? It depends. Cummins Filtration suggests every 200k miles or 6,500 hours. Detroit suggests 3 years or 500k miles. Our recommendation? Change the filter at least every 3 years. If you are putting more than 35k miles on a year, try to have it done every 100k miles. The manufacturers recommendation is safe and in no way wrong. We feel for the price of the replacement filter, it’s good practice to replace more often and mitigate issues with more expensive doser injectors or pumps down the road.