Okay... just did the whole thing. The result was not quite like i'd hope. It might be because I didn't use the product in its pure form (30%diesel+70%STP diesel injector cleaner, not counting the amount of diesel inside the fuel filter). There wasnt any visible 'cleaning' as evidenced by the lack of grime that should have returned to the jar. There also weren't any noticeable changes in the engine's performance. But then this could all be due to the fact that I am quite religious in changing the fuel filters. I'm going to give it another shot, this time using the pure form. Be back again.