According to Amsoil, although not Mobil 1, with synthetics you can go longer than 3 months or 3K miles between oil changes. Go to their website and check it out. As long as it is not black and smelly, you should be fine though. Synthetic is a good choice. I'd used synthetic for more than 1/2 the life of my motor before rebuilding it - I put over 125K on the motor within 3 years. When I disassemble the engine it was clean, even so clean that the machine shop thought that I'd already cleaned the engine when I took it to them for machine work.
