Could it be that the EGR sensor is malfunctioning or the EGR valve? My understanding was that there should be conditions under which the exhaust gas is recycled to the intake system, but for some reason, the valve is staying open, so it's happening all the time. So that's not good. Because the ECU will reduce the impact on your engine, you might not realize anything is wrong until it breaks. For that reason, a warning light is present. Would premium fuels or diesel additives work? Between dpf regenerations, how far do you typically drive and how long do you typically let it run? About 160 miles and 444 minutes of mining.