There's so much more to it Bartamos. Vehicles that aren't driven much have there own issues, from moisture in the oil to the oil actually becoming acidic and eating bearings.

Here's a good article related to oil changes: http://www.waynesgarage.com/docs/oil.htm

On my daily driver I change the oil every 8000 miles, using Mobil One.

On my classics once a year.

An oil change is cheap insurance....