Use your DIC as a guide to change oil or GM alternative change schedule as outlined in your Owner's Manual. Over the years, the machining capabilities of engine manufacturing and the advancement of oil technology has made more frequent oil changes unnecessary, an additional unnecessary expense to you and ecologically unfriendly. I am far from a "tree hugger" but they are the facts. Changing oil every 1,500, 3,000 or 4,000 miles, just based on mileage alone is now a farce. This is no more needed than re-pack wheel bearings every 10,000 miles or get a full tune up every 12,000 milles. We still don't do that do we?
GM has installed a state of the art computer system that detects the type of operation you perform from the temperature to trip length and even your RPM operation every time you drive to figure when to change oil and filter. USE your DIC, change your cartridge type filter with a quality unit (AC-Delco) and use GM Spec oil and you will be fine! Brand depends on what YOU like and what YOU are loyal to. Again as long as is GM Specs. Taking full synthetic or any oil and changing it every 3,000 is just a waste of time and money. (Your garage will like you though)
Again, all will have a different opinion,,, your car came with conventional oil. Use conventional for 1st or 2nd regular changes and if you wish to switch to synthetic or a syn. blend, that's fine. This allows valves and rings to fully seat prior to synthetic (in these engines). It appears, if this does not occur properly, excessive oil consumpion will occur, more as miles accumulate. It is not recommended you mix both types of oil at the same change.
Keep in mind everyone has their own "formula" to do it their way... what the've heard or what they've been told.... "from their Grand-Dad to the friend of a friend that used to live next door to a world famous engine builder!!
Use your GM Owners Manual and good old Common Sense and you will be fine.
Enjoy your Cobalt.. It is a nice little car that will give you years or trouble free service if taken care of and maintained properly!!
If You're SCARED... SAY You're SCARED...