My car has recently encountered a significant problem with excessive fuel use. I previously achieved a minimum of 450 miles on a half tank, but now I am only attaining approximately 300 miles at best, and I am uncertain as to the reason. The vehicle receives a full tank and undertakes a 300-mile motorway excursion weekly.
I regularly undertake extended motorway drives at 70 mph for over three hours, so I doubt it could be the DPF, although I am not totally certain. I previously had an exhaust back pressure sensor problem that resulted in a powertrain fault on iDrive; however, after replacing the sensor, the vehicle no longer displays that fault. I have poured DPF cleaner to a full tank and executed another thorough drive on the freeway, but to no avail. I have recently undergone a significant service that has yielded no results.
I consulted BimmerUtility, which indicates my soot levels are at 45.99g. I have observed this value decrease to 8g, but it occasionally spikes to the high teens or abruptly returns to approximately 45.99g. I previously had a 24C800 error, which was resolved by replacing the sensor. However, I am now facing a 25C800 error. Does this indicate that the DPF need replacement and is it the source of the problem?