Spot on DJ! As I tend to change my coolant on a time basis rather than milage I am happy staying with the original spec OAT. Ford as you say have upgraded and say this is compatible for use in their previous systems specced for OAT. But I've been around long enough now to have seen the reports that only time can show up where components breaking down due to reactions have happened. E10 fuel for example, blimey what a mess that created.
But I was surprised to see the sediment issue my car had thrown up this time. Its low milage and well serviced. Thinking about it, it was probably due to the OAT coolant mix throwing sediment, (Looked much like a red wine that had thrown a sediment in the bottle), over the total life of the car. When all surfaces were coated the new sediment found it harder to adhere to the already coated surfaces so made their way to the header tank. Now the latest coolants don't hold an electrical charge, the older types do, in fact you can use a multimeter to read it! So, when the metalled surfaces were coated, a little like powder coating paint finishes, the sediment then remained in suspension in the fluid. Well, I don't know this to be the case, just a theory. The hoses incidentally were as clean as when new but the initial drain down produced a new looking coolant mix yet the subsequent clean with the flush washed out like filthy ditch water and took three more flushes to run clear. Over the years I have flushed many a system using the old hose method and didn't achieve much in the way of discolouration to the water. Since using Prestone for the last few years on our cars as they aged I have been very pleased with the results of how they cleaned the system...... however I was not expecting a 10,000 mile mog to produce anything much... Oh how wrong I was!
