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2010 Chevrolet Cobalt Oil Change

2010 Cobalt 2.2 4 cyl Ecotec with 57k miles. Had a senior moment with the oil change. Discovered I had used Valvoline 5w20 instead of 5w30 afterwards. Car not driven hard, OLM usually recommends a 9 to 10k oil change interval, I use a 5k interval.

Any reason to be concerned? I’ll go back to 5w30 next time.



No reason to worry.

Considering it is summer, and the higher number is hot oil viscosity, and you used a lower number (lower viscosity) I’d say change it. Don’t worry about the filter.

If it was winter, I say you could get away with it.


Mustangman and I just proved why asking oil questions is almost a waste of time. There are so many different opinions that they could not be counted.

Edit: seriously, if you are asking then you might wakeup in the middle of the night worrying about the oil. Not talking about a lot of money so just do what makes you feel good.

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What does the owners manual say? Lots of cars are good with 5W20 these days.

It doesn’t matter if it’s winter or not.

The 5W is the WINTER weight.

Once the engine comes up to operating temperature, that decides if the oil becomes 20 or 30 weight.


Where do you live?

Arizona: Change it out now.

Alaska: Leave it be.

This probably isn’t a big deal. If you had used a 20W50 I would have said change it now for sure. Oils seem to get better each year and the newest 5W20 may exceed the protection of a 5W30 from 2010. I don’t know if this engine uses any type of variable valve timing but would be concerned about that and the hydraulic lifters if you went too thick.

On the other hand, if you had gone slightly thicker such as 10W30 this probably wouldn’t have been much of an issue either. I wouldn’t do it in cold climates but being summer, you might have been fine. Look at the manual and see what alternatives are if the suggested 5W30 isn’t available.

Then there are cars made for sale in different parts of the world. My Mitsubishi Mirage is one of those. It calls for 0W20 in the US, largely because of fuel economy concerns. The manuals in other countries allow for anything all the way up to 10W40. The engine internals are the same no matter where these are sold.

Look to your Owner’s Manual for the best advice. Often, they will have a table showing various acceptable oil viscosity for a given ambient temperature. The lower the ambient temp, the lower the viscosity allowed. Those often overlap a bit. But your Owner’s Manual is very specific in this regard and calls out only one viscosity specification and has some verbiage addressing alternatives:

This is a tough one, thanks for all the suggestions. Once the Cobalt warms up the engine temp is ~195 in the winter and between 195 and 210 in the summer.

It doesn’t use any noticeable amount of oil between 5k changes. Since the 5w20 is thinner I will keep an eye on the level and change it if it starts to drop. If not I’ll change the oil at 3k or so.

Again, thanks.

Ed B.

On some designs, the oil is not just lubrication for the engine internals, it also serves as a hydraulic fluid for actuating parts like a variable cam phaser for example. In those instances, oil viscosity can be much more important. I have no idea if your engine uses the oil in this way but something to consider and look into for your specific situation. I doubt it’s going to cause issues, especially if you change it that soon. Just like to make informed decisions myself.

Yes, checking level more often would be wise.

If you engine sports variable valve timing, and the oil spec you used isn’t listed in the owner’s manual, suggest to replace it with the correct oil. You can drain it out and use that drained oil for your lawnmower or general lubrication needs. I should make for a pretty good light general purpose oil.

I wouldn’t go that far. Asking about subtle differences may be a waste of time, but there are many who have no clue about oil and answering their questions can enlighten them in ways that can save their engines. I would not discourage anyone from asking.

Regarding the OP’s question, a look in his owner’s manual may even disclose 5W20 as an optional choice.

The difference between 5W20 and 5W30 is a slight difference in the amount of “viscosity modifiers” added to the base oil. “Viscosity” is a measurement of a fluids resistance to flow. Oil gets thinner, its viscosity drops, when it gets hot. Oil refiners add microscopic coiled polymers to the oil that expand (uncoil) when they heat up, counteracting the tendency of the oil to get thinner. The modifiers don’t lubricate as well as the oil, however, so the amount added is “just enough” and the difference in the base weight and the modified weight typically never exceeds 30. You’ll see “10W40” occasionally, but not often. 10W30, a variance of 20, is considered acceptable.

If you live in Nevada, New Mexico, or Arizona, I’d recommend changing it just to have as much of a “buffer” as possible. It gets doggoned hot there.
If you live in Montana or Oregon. you’ll be fine. It just doesn’t get that hot there.

You can look at it 4 posts above yours. It is very specific- only 5W30.