Right now I'm at 4 months with 4000 miles on this oil and this stuff is very clean; although, I already have a very clean engine so it may not darken as much as it might in someone elses engine. And my driving conditions are not dusty at all. This is not scientific, but my fuel gauge is much slower to go down on this stuff compared to others I've used like Castrol GTX and Pennzoil (pyb). I've heard mixed reports about the add pack not being very good compared to the older version (Mobil Clean 5000), but I'm trying to disregard the VOA and UOA reports given technology in todays oil such that none of us really can be fully aware of an oil's capabiliites simply by looking at one of these reports. Is anyone else using this? Do you like it to?