[me and my metro]

I would look in the recommended maintenance section of your owners manual. I always follow the shorter intervals that are recommended for city/taxi use. Even if your car only sees highway use I would use the city interval.
If there is no recommended oil change interval then 30k miles should be ok. CVT is a great idea in theory however in reality they have been somewhat troublesome. I would love to hear how the success stories CVT cars are driven. I would bet that people who drive for economy have much better success with these transmissions and vehicles in general.