Chilean Car, 6 months "visa". Is this extendable?

We´ve bought a beautiful kombi to enjoy South America in. We drove from Santiago to Buenas Aires and at the border we got a 6 months "visa" for the car. We want to travel up through Brazil before returning to Chile to sell the car. And without the stress of our cars visa to run out and having to rush back or face tough problems returning at the border over due date.

Have you guys got any experience with this? Can we extend the visa in any ways?