Yankees1,
I've been using Amsoil for almost 25 years, but if you are dead set on changing oil every 3000 miles, I'd run Mobil 1, 5w-30. I prefer the 5w-30 over the 10w-30 for an over head cam engine, as it is important to get sufficient oil flow while the engine is warming up. Actually, I'd run the Amsoil 0w-30 in this motor, with a 7500 mile change interval if I drove it really hard.
I am close to buying a 1994 Porsche 911 Targa, w/ Tiptronic for my wife and will probably run the Amsoil, Series 2000, 0w-30 in that motor in the winter, and the Amsoil 10w-40 in the summer. This 3.6L motor has a dry sump and holds about 10 quarts of synthetic - they all come with Mobil 1 right from the factory ....Not as fast as a Vette, but the handling is incredible, if you don't mind hanging the tail out and never lifting or braking in the middle of a turn ....The brakes are amazing as well - it feels like a giant hand has reached down and grabbed the car.
TS