I've noticed the injectors tend to coke up from running cold. So, I only run the WMO blend when the engine is fully warmed up. I like to use it for long highway trips. But even then the injectors tend to coke up.
I think it is because the engine runs so damn cool. I even have a 203* thermostat in it. I'm talking about the 1st '97 in my sig. The WMO requires more advanced timing because it is slower burning, but you can't change the timing on the PowerStroke like you can the IDI. Maybe some day...
The engine runs so cool, I have taken the engine fan off. I even have the front grill mostly blocked off! I was expecting the engine to run hot because the temperature on the weekend here was above freezing. Nope, not the case! And that is running on D2! I don't run the WMO in the winter. I don't need those kind of problems in the winter.
That being said, my son is running my project truck which has a tank of WMO blend in it. He told me it runs great! He thinks it makes more power than the D2. I wasn't going to run the WMO in the winter, because that truck has a 6.0 electric fuel pump in it, but it seems to be handling it.
When the injectors do get coked up, I add a few litres of biodiesel to the D2 tank and run it hard/hot. That seems to work. Biodiesel is a fantastic cleaner!
I saw an earlier reference to me having problems with WVO sludge. It was not WVO sludge. The problem I ran into was polymerization of the biodiesel. Over time, when exposed to oxygen (air), the metal fuel tank acts as a catalyst to polymerize the RME (Rapeseed Methyl Ester) to make polyester. If you are going to use biodiesel, use it quickly. Store it in plastic barrels/containers, and try not to expose it to oxygen.
The WMO-WVO sludge is fairly well documented as mentioned in previous posts.
Happy motoring.