I haven't tried their oil products, but I use their fuel additive religiously. It gets me about 5-10% better mileage and restores the lubricity of the fuel removed along with the aromatics. It will be in the GTO from the first tank.
As for oil, I plan to change the factory fill as soon as I get it home, fill up with good quality dino oil and a break-in additive containing soluble molybdenum which reduces shearing of rough contact surfaces. After break-in, it'll be Mobil 1, and at around 5K miles, I'll start adding 4 Oz Tufoil at each oil change. At that time, I'll change transmission and gear oil to synthetics, and add a small quantity of Tufoil there too. The combined effect should noticably reduce power losses in the engine and driveline.