Why would you ever want to run 10W-30 over 5W-30?

[Stopsign32v]

I've always wondered this and never have figured it out.

Assuming you keep your RPMs below 2,500 until the car warms up, what would the point in running 10W-30 over 5W-30? If anything I would think you would want to run 5W-30 over the other to get oil to the valvetrain faster.

When up to operating temps when you would go wide open throttle, both oils are the same weight.

 

[gfh77665]

Lower viscosity spread.

 

[Burt]

When you live in a warm climate, the greater range doesn’t matter in terms of start up oil flow/pressure. Also it used to be that the narrower the range the more stable the viscosity over time. I don’t know if that is still the case.

 

[Barkleymut]

Because I scored a bunch of 5 gallon jugs for $2 each. Most were 10w30 and it never gets below 15 F here

 

[addyguy]

In warmer temps, the 10W-30 is slightly less volatile, and will most likely shear less, so it will reduce consumption and possible wear from thinned out oil.

 

[Stopsign32v]

In warmer temps, the 10W-30 is slightly less volatile, and will most likely shear less, so it will reduce consumption and possible wear from thinned out oil.

How does 10W-30 stand against 5W-40?

 

[slacktide_bitog]

when it's on clearance

 

[Chris142]

My jeep owners manual says only to use 5w 30 below 0f. Sounds weird to me but whatever.

 

[kschachn]

I've always wondered this and never have figured it out.

Assuming you keep your RPMs below 2,500 until the car warms up, what would the point in running 10W-30 over 5W-30? If anything I would think you would want to run 5W-30 over the other to get oil to the valvetrain faster.

When up to operating temps when you would go wide open throttle, both oils are the same weight.

The winter rating is about cranking and pumpability, not flow. Such a common misconception.

And it’s highly dependent on temperature. Depending on the temperature there’s no guarantee any particular oil with a 5W winter rating flows any better than one with a 10W rating. Again not that flow really matters here.

 

[Jetronic]

I've always wondered this and never have figured it out.

Assuming you keep your RPMs below 2,500 until the car warms up, what would the point in running 10W-30 over 5W-30? If anything I would think you would want to run 5W-30 over the other to get oil to the valvetrain faster.

When up to operating temps when you would go wide open throttle, both oils are the same weight.

All else being equal

the 10W-30 has less viscosity modifiers which are not 100% shear stable and cause deposits
the 10W-30 is less volatile
the 10W-30 has a higher base oil viscosity mix, which timing chains love.

If you can get a synthetic 10W-30 and the temperatures in your area are high enough to use it (above 0°F at all times), I see no reason to use 5W-30

 

[Stopsign32v]

All else being equal

the 10W-30 has less viscosity modifiers which are not 100% shear stable and cause deposits
the 10W-30 is less volatile
the 10W-30 has a higher base oil viscosity mix, which timing chains love.

If you can get a synthetic 10W-30 and the temperatures in your area are high enough to use it (above 0°F at all times), I see no reason to use 5W-30

What about 5W-40 instead of 5W-30? I run Rotella T6 and they have 10W-30 and 5W-40. (not sure why they don't have 10W-40)

 

[kschachn]

My jeep owners manual says only to use 5w 30 below 0f. Sounds weird to me but whatever.

That’s an appropriate winter rating below 0F. I wouldn’t use one with a 10W below 0F.

 

[Rand]

All else being equal

the 10W-30 has less viscosity modifiers which are not 100% shear stable and cause deposits
the 10W-30 is less volatile
the 10W-30 has a higher base oil viscosity mix, which timing chains love.

If you can get a synthetic 10W-30 and the temperatures in your area are high enough to use it (above 0°F at all times), I see no reason to use 5W-30

except all else is likely not equal.

 

[OVERKILL]

Lower viscosity spread.

I mean, technically it's typically a wider viscosity spread (10W-30 will have a lower VI typically, so the spread between KV40 and KV100 will be wider, along with at other temperatures), but there's a lower grade spread between the Winter grade and the SAE grade.

 

[Bkdc]

I don’t see any practical reason except for improved shear stability. If you run extended oil change intervals….. But frequent oil change is always a good thing.

 

[Jetronic]

I don’t see any practical reason except for improved shear stability. If you run extended oil change intervals….. But frequent oil change is always a good thing.

higher MOFT will help even then, if the oil film thickness exceeds the debris size, no wear.

 

[Jetronic]

What about 5W-40 instead of 5W-30? I run Rotella T6 and they have 10W-30 and 5W-40. (not sure why they don't have 10W-40)

depends on the appication. When hot, the 5W-40 will protect better, but expect higher volatility and more viscosity modifier

 

[Stopsign32v]

depends on the appication. When hot, the 5W-40 will protect better, but expect higher volatility and more viscosity modifier

Man I got a long way to go when it comes to learning oil.

Ok so volatility, you are saying I will lose more oil with the 5W-40 over 10W-30? If so I have no concern here because I check my oil weekly or bi-weekly to make sure the level and color is fine.

Viscosity modifier...I have no idea what that means.

 

[Jetronic]

Man I got a long way to go when it comes to learning oil.

Ok so volatility, you are saying I will lose more oil with the 5W-40 over 10W-30? If so I have no concern here because I check my oil weekly or bi-weekly to make sure the level and color is fine.

Viscosity modifier...I have no idea what that means.

volatility could lead to intake tract deposits, but to be fair I consider it more of an indication of the base oils used and what those could or couldn't do.

viscosity modifiers are added to make oil less thin than they would be when hot. Strip the viscosity modifier from a 5W-40 and you likely end up with a 0W-20.

J

Thread 'Castrol 5W-40, QS 5W-40, QS UD 10W-30, Amsoil SS 10W-30 Volatility Results - Dec. 2024'

Dec 18, 2024

Castrol 5W-40 (C 5W-40), Quaker State 5W-40 API SP (QS 5W-40), Quaker State Ultimate Durability 10W-30 (QS UD 10W-30), Amsoil SS 10W-30 (Ams SS 10W-30).

Please see the following two threads about past results.
https://bobistheoilguy.com/forums/t...rotection-volatility-results-nov-2024.389905/

The test procedure was like the previous except the oil temperature was ~420 F throughout entire test. Also different is...

• JAG
• Replies: 1
• Forum: Passenger Car Motor Oil (PCMO) - Gasoline Vehicles

• 

 

[Merek]

I used to run Chevron Delo XLE 10w30 in my Civic years ago, you could get it at Walmart for $12-$13 jug back then. I experienced the lowest consumption when running that oil. Sometimes during winter it can drop into the teens but typically doesn't stay there long but never had an issue.