Oil Spec

Do I should change to another SPEC with the time?

No, just replace the old oil with new oil of the same type as it has a set life time depending on the engine and driving conditions (hence the suggested time to replace). General information should be available on the side of the oil container or from a local auto mechanic, or in the example link below if you are confused as to what type to use for your vehicle and application.

http://en.wikipedia.org/wiki/Motor_oil

Although this post technically violates Rule #75 because it contains two sentences, I believe that it still falls within the general guidelines.

I've heard of this idea, but I don't know if it is true. The purported rationale is that as the piston rings wear and develop some greater clearance, a heavier oil will seal better. If so,in your case you might go to 20W-40. Does the engine manual mention anything like this?

Adhere to the OEM specifications.

Remember that the best oil for any engine is clean oil.