what type of motor oil to use
10W30(summer) or 5W30 (winter) although its recomended that you use 10W30 at all times
use whatever the car suggests to use. it should say on the dipstick or oil cap. oils are so advanced from before they wont break down as fast so there is no need for heavier weights in the summer than winter anymore
Agree with all the previous post. From what I have seen on these motors, 10W-30 were the reccommended oil until the Series III engine, first launched in MY 2004 Pontiac Grand Prix. According to the GM Powertrain website, it was not necessary to use 10W-30 and that 5W-30 oil was okay on 3.8L Series III engines. As to why the change is okay, I am still trying to understand.
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