Different Summer and Winter Grades

[Gene K]

Different Summer and Winter Grades
Car rated for 20 and 30 Grade

Typical Summer and Winter Oil Temps
30 grade = 12.33 cSt @ 95C
20 Grade = 12.37 cSt @ 85C

Any reason not to run 30 Grade in the summer and 20 Grade in the winter?

 

[kschachn]

Those aren’t “summer and winter grades” unless you’re just making the distinction yourself.

 

[BMW Dom]

 

[Duffyjr]

 

[Gene K]

Those aren’t “summer and winter grades” unless you’re just making the distinction yourself.

I was making a distinction between a different grade for the summer and winter not SAE 20 vs 20W. I added the omitted word in the title and OP to make it clearer.

 

[PimTac]

They used to call for this like 70 years ago or soon certain regions. The advent of multi viscosity oils pretty much eliminated this.

Back then people were changing oil more often than today. Today, run the grade that your owners manual recommends with no worries.

 

[ZeeOSix]

Different Summer and Winter Grades
Car rated for 20 and 30 Grade

Typical Summer and Winter Oil Temps
30 grade = 12.33 cSt @ 95C
20 Grade = 12.37 cSt @ 85C

Any reason not to run 30 Grade in the summer and 20 Grade in the winter?

Hair splitting. Why go through the trouble of changing hot temp viscosity rating because the oil runs 15C difference between summer and winter? Stay with xW-30 grade and enjoy the HTHS headroom.

 

[Gene K]

Hair splitting. Why go through the trouble of changing hot temp viscosity rating because the oil runs 15C difference between summer and winter? Stay with xW-30 grade and enjoy the HTHS headroom.

Why not if it's being changed anyway? That's what I'm asking.

 

[Lubener]

Gee, I am glad I use a multiviscosity oil so I don't have to worry about this and sleep peacefully at night..

 

[PimTac]

Why not if it's being changed anyway? That's what I'm asking.

Are you using straight grades like SAE 20 and SAE 30?

 

[Gene K]

Are you using straight grades like SAE 20 and SAE 30?

No, they would be multigrades like 5W-20 and 10w30 (used for example). You could change it to 10W-40 and 20W-50 if you want. My question is simply if the viscosity is the same at sump temp does that hold up once you start talking about the viscosity in the bearings?

 

[PimTac]

No, they would be multigrades like 5W-20 and 10w30 (used for example). You could change it to 10W-40 and 20W-50 if you want. My question is simply if the viscosity is the same at sump temp does that hold up once you start talking about the viscosity in the bearings?

You are way overthinking this. Run a 30 with the winter rating that fits your local climate. A 5w30 will pretty much suit any weather. Run it year round.

 

[Jetronic]

Why not if it's being changed anyway? That's what I'm asking.

Those typicalo values are fine, but what if you push on a bit and the oil temp goes to 105-110C? If that can't happen you're good.

 

[Dave9]

Decatur, AL. use -30 all year round.

 

[Gene K]

Those typicalo values are fine, but what if you push on a bit and the oil temp goes to 105-110C? If that can't happen you're good.

Well both are supposed to be fine. I still remember Corvettes running 5w30 to 150C on the track with no oil cooler. Scared the crap out of me.

 

[kschachn]

No, they would be multigrades like 5W-20 and 10w30 (used for example). You could change it to 10W-40 and 20W-50 if you want. My question is simply if the viscosity is the same at sump temp does that hold up once you start talking about the viscosity in the bearings?

That's why there is the HT/HS. Which is a whole lot more representative of behavior during engine operation.

 

[Bill_W]

We can take pot shots as well as you can. Your operator’s manual has an ambient temperature chart. Notice for a modern engine they all show the same “high” ambient temp suggested for all viscosities. That has to do with your car engineered for it. The low is the one you need to worry about.

 

[Gene K]

That's why there is the HT/HS. Which is a whole lot more representative of behavior during engine operation.

Yes, but does sump temp follow through to effect bearing temps. I would think it does because they usually recommend different grades for different max sump temps on track cars.

 

[JohnnyJohnson]

The only reason I've done this I wound up getting some Pennzoil 5W-20 for $4 a Jug. Ran it for my winter OIC and it was just fine. No complaints from the Corolla.

 

[ZeeOSix]

Yes, but does sump temp follow through to effect bearing temps. I would think it does because they usually recommend different grades for different max sump temps on track cars.

Yes, the temperature rise in the bearing will be X degrees above the sump oil temperature, assuming all other variables are constant (engine RPM, load, etc). If the sump is colder, then the max oil temperature inside the bearing will also be lower compared to if the sump temperature was higher.