I,ve been using it in my gmc for about the past 2 months and I really like it. I have the vortec 5.7 liter and my oil pressure stays constant, plus it's still relatively clean looking.
At $6.00 a gallon it's hard to beat!
I've been using it for the past 2 months in 2 cars...
the daily driver Bonneville a relative uses and my solo II race car.
Quieted down the upper end on the bonneville and I haven't had it in the Z long enough to really tell anything. Also I'm in the process of doing an autoRX on it...
Once I'm done doing the autoRX and using up the cheap oil for my beater I'll put it in there and see if it silences the top end of that car.
Grease is the word; I started using diesel oil in my Mazda 626 2.2 I-4 when it hit 120k and was using a quart per 3000. The additive package cleaned up the internals, and now I only burn (and weep-need a valve cover gasket) a quart per 5 to 6 thou. Hope you get the same results.