I don't know what section to post this particular question at.

The manufacturer suggests that you use 5w30 oil for the 2.2 Ecotec, but what if the mechanic puts in 10w30 instead?

I am in Arizona, and it is never cold here, so that is a factor to this question.

I do not want the engine to get damaged.

 

well you see..........i have no clue

 

if GM finds out they will void your warranty... just FYI so if your engine does take a crap on you be sure to do a quick oil change and explain to them you dont know what happend. BUT thats if something does go wrong

 

I know if I had straight 40 or 50 weight, that engine would be trashed.
But this is only 10w30 vs 5w30 for one oil change.

This is what I found on the net:

5W30 versus 10W30
Virtually all new passenger vehicles sold in the U.S. use either 5W30 or 10W30 oil. The difference between the two is that the 5W30 flows better when cold, so if you live in a cold climate or operate your vehicle in a cold climate during the winter months, you should use 5W30 if it is the preferred oil for your vehicle. If you live in a sub-tropical climate and don't operate your vehicle in cold climates, then 10W30 is acceptable as long as the manufacturer specifies that it is permissible to use it.

Is there a disadvantage to using an oil that flows better when cold, i.e. 5W30 versus 10W30?
Sometimes, but usually not. The crux of the issue is this: the bigger the difference between the cold oil viscosity and the hot oil viscosity, the more the volume of viscosity modifiers and the less the volume of base stock. If you are good about following the manufacturer's recommended oil change interval then stick with the 5W30 if that is the preferred oil for your vehicle, even if 10W30 is acceptable in warmer climates. Older cars may specify 10W30 only. This is because they need a little more viscosity when cold to keep a protective film on the cylinder walls. There have been instances where the larger amount of viscosity modifiers that are present in 5W30 have broken down due to excessive heat and have left carbon deposits on the valves, but this is extremely rare. The proper fix would be to reduce the excessive heat, but the workaround was to use an oil with less viscosity modifiers.

 

Living in Arizona you are fine. Here in Ohio 5W-30 is recommended and sometimes it gets below zero for a few weeks straight in the winter.
The difference between 5W and 10W is almost nothing anyway.

Did you understand what you just quoted off the net? Basically, the 10W has more oil, and less viscosity modifiers per quart. Some people would say that 10W-30 is better in a climate as mild as yours, no matter what GM says.

 

there is no problem using 10-30 in your motor. Most shops in az use 10-30w for oil changes.

 

Thanks guys, I had a bunch of people on j-body.org saying that the motor will blow up and all sorts of non-sense with 10w30.

 

No, it won't blow up, though I would recommend specifying 5w-30 from now on, and not letting GM know about this.

 

i accidentally mixed 2 quarts of 5-30 with 4 quarts of 10-30. and it worked fine. (my dad bought the wrong quarts)

 

it wont make a difference.... i have 10w30 in my car right now and i live in wisconsin.. i switch to 10w30 in summers and 5w30 durning winter not like it really makes a huge difference

 

I've run 10-40, 10-30, 5-30 and 5-20, doesn't make a difference, especially in warmer climates. The only reason to go real thin is for better viscosity in cold weather, heavier oil robs more power due to friction loss but is better for your engine because it generally retains a heavier layer on cold starts.

Best bet is to make sure you are getting a quality oil rather than worry about the weight. Use Mobil 1, Castrol GTX, something like that, and the viscosity becomes irrelevant as far as engine protection goes.