Just to let the audience know. I have had the Castrol Synblend GTX in my Nissan for over 3,000 miles now, and it is running very smoothly. The engine is quiet, I would state even quieter than when I was using Mobil 1 w/Purolator PureOne Oil Filter. Now it has the Castrol Synblend GTX oil and the plain Purolator Oil Filter, and it seems, to me, to be running very quietly. Maybe it is my imagination, however, the engine runs very smoothly under my lead foot. I checked my oil yesterday, it is at the same level as the day the oil was put in the truck, a little darker, but not by much, still can see the marks through the oil on the dipstick.