I checked
Motor Oil Myths and Facts
and they said that "Synthetic oils withstand higher temperatures before breaking down, and have more base stock and less viscosity modifiers. Synthetics wear out, become acidic, and eventually become saturated with suspended soot particles, just like regular oil. Again, an oil analysis is a good investment to determine the optimum oil change interval. Never exceed the manufacturer requirements for normal service."
So, it sounds like there are the same oil changes required. But that site also pointed out that our country (USA) has always recommended too many oil changes and the new oils don't really require it. Maybe I can just start changing the filter once a year and adding a quart of this synthetic fluid. They used Pennzoil Synthetic 5W30.