oil changes or changing oil

[mrcoffee]

i like to do my own oil changes just baught this 08 cobalt ..i think dealer was using mobil reg oil...now i have some left over quarts of valvoline max life synthetic blend 5w30 that i used on my other older higher miles car...
my cobalt only has 21000 miles ive heard stories that you should only use any synthetic oil when you have higher mileage...so any experts out there know what i should do...like buy some reg 5w30 oil not being synthetic for now or is it all ok to use the synthetic blend... ive heard that the synthetic is way more durable but things mite not seal as good when lower mileage and not completely brokin in yet... thanks any info will help me decide..

[YelloEye]

My car has been running Mobil1 5w30 synthetic since it left the factory 30k mi ago.

[reyesa21]

i have no idea what oil is in mine. i hav 29,000 on my balt and im due for an oil change so i will tell you what they put in it

[Tuner923]

I am fairly sure that your owner's manual will state what viscosity and what type of oil is to be used either conventional, synthetic or blended. :P now that being said. either or is fine as long as its the correct viscosity. the only difference between synthetic and conventional oil is conventional breaks down faster then synthetics. synthetic oil can be ran safely for more miles than you'd think with out an oil change, some people say don't go past 7500 miles. BUT this will void your warranty. I personally change every 3k with full synthetic 5w30