5w20 in an 08 Buick LaCross 3.8 (5w30 standard)

[Hermann]

Run it, it will work just fine. Run a 5W-30 for 2-3k, and it will most likely shear down to a high 20-weight, so what is the difference?
It’s been running a sheared-down 20-weight for years!

Your beat me to it.

 

[JavierH19]

I scored 6 jugs of 5w20 on Amazon for $4.60 each incorrectly thinking that was the correct oil for the vehicle.

It's not about fuel economy, just using what I have on hand, which is starting to seem like a bad idea.

In this case I'd use it. Maybe throw a quart of 20w-50 in if you want.

 

[Hermann]

Just use it like it is. It is a High Mileage oil, made a bit stouter. IMO

 

[Bill7]

I would recommend Pennzoil Platinum Full Synthetic High Mileage 5W-30 in 5 quart jug from Walmart for $26.
The HTHS = 3.2 will provide more engine protection should you encounter severe service. I would also use Fram Ultra oil + air filters with 99% efficiency @ 20 microns. With this combination, it might be possible to get 200k or even 300k miles out of that car.

 

[Slick3914]

Add a quart of Lucas and you’re good to go.

 

[kschachn]

Run it, it will work just fine. Run a 5W-30 for 2-3k, and it will most likely shear down to a high 20-weight, so what is the difference?
It’s been running a sheared-down 20-weight for years!

We’ve seen very few instances of sheared oil on here.

 

[nickaluch]

It's fine you can add half of a small container of STP oil treatment to thicken it up

 

[GR_CoB]

Aren't Amazon Basics and Supertech both made by Warren? I'd just grab some ST 10W-40 (or maybe even 20W-50) and mix with AB 5W-20 at a 50/50 ratio. Ad-packs should be similar, no? Should be a better option than Lucas or STP.