First OCI with Rotella T6, running in the winter, with a lot of overnight idling. Transporting RV's for 2 months, 50% towing, 50% running free. Polaris Comments: Flagged data does not indicate an immediate need for maintenance action. Continue to observe the trend and monitor equipment and fluid conditions. Cylinder region metals (pistons, rings, liners etc.) are at a MODERATE LEVEL; Viscosity is MODERATELY HIGH. Causes include contamination, oxidation, incorrectly identified viscosity grade, or adding a different viscosity grade to the component. Base Number is SLIGHTLY LOW. As Base Number depletes, the ability to neutralize acids is diminished. Soot is at a MINOR level and is not yet cause for concern. Monitor future samples for increasing levels. Elevated soot reduces combustion efficiency and may indicate varying load conditions, malfunctioning EGR, exhaust restriction, or a timing/air-to-fuel ratio imbalance. HIGH SOOT LEVEL is interfering with FTIR spectrum (Oxidation, Nitration). Lubricant and filter change acknowledged. The big issue with this oil sample is the Iron reading of 159. But I have a possible explanation for it. I was using the Better Diesel FBC (Fuel Borne Catalyst) fuel additive for nearly this whole OCI. The Better Diesel additive has iron content in it, and they do say that it shows up in oil analyses. The example that they show on their website didn't show nearly as much Iron as mine does, though, so it is something to watch on the next sample. I used the FBC to clean out the DPF, and it seems to have worked. Before I started using it, I was getting about 8.5 mpg while towing. As I used the FBC, fuel economy steadily improved to about 10 mpg towing. The recommended dose is 1 oz per 25 gallons of fuel, and I used up my first shipment of it in about 20k miles. I will not use the FBC on this OCI, and see if the Iron goes back down. I was fretting about a turbo screech problem a couple of weeks ago, and I wanted to do this oil analysis to see if turbo thrust bearing material was present. Fortunately, Copper is low, so my fear seems unfounded. I also took off the turbo inlet tube last week and checked shaft end play, and it was tight. Soot is up to 2.4% for this 20k mile interval, compared to 1.2% for the previous 10k mile interval. Double the miles, double the soot, so it seems to act linearly. But I'm cursing the EGR; my old truck never registered soot over 0.7%, on OCI's up to 37k miles. Still no fuel dilution, and this is good news considering the large number of trap regens that it has had on long overnight idles. This was one of my concerns when I got this truck. So my only complaint is the large amount of fuel burned in the regens. The KV100 of 17.5 is considerably higher than the virgin KV100 of Rotella T6, which should be ~15.4. And Polaris is complaining that the Oxidation number is being interfered with by the high soot. So maybe the oil has oxidized? On the other hand, Polaris has had the occasional spurious reading on viscosity in the past. The other possible cause they list for the high KV100 doesn't wash: I know I put RT6 5w40 in it. Polaris is tagging the 3.0 TBN reading as slightly low, and that seems about right. Recent VOA of RT6 15w40 had TBN of 8.3, and Polaris recommends changing at 35% of virgin, so this oil was due for a change at 20k miles.