What would the Normal "warmed up" oil weight be?

[ZZman]

We talk about weights on oil on here and alot about cold weights of oil.

My question is: After a vehicle is warmed to operating temp what would the weight of oil be? Similar to a 20 or 30 weight in thickness? Or would it go to the highest viscosity number it can go to for the oil like a 40 or 50 weight?

 

[StevieC]

If an Oil is a 5w30 then it's a 30wt oil when hot but pumps like a 5wt when cold. It's always a 30wt oil. You can get this information off the MFG's website. Look at the CST value. Most 30wt oils are 9cst when warmed to 100oC.

Hope this helps...

 

[Quattro Pete]

Originally Posted By: ZZman
My question is: After a vehicle is warmed to operating temp what would the weight of oil be?

The weight doesn't change. The viscosity changes on a curve specific to the given weight.

Manufacturers state what the viscosity is at 100 deg. C. - you can find it in the specs. However, depending on your specific engine, your typical operating oil temp may be lower or higher than 100 deg. C.

We had a link to a viscosity calculator here somewhere, however, it is only an approximation. Maybe someone can post it again.

 

[Bryanccfshr]

The best way to express viscosity is in cSt or centistokes http://www.sizes.com/units/centistokes.htm

Operating temperature viscosity will depend on what the saurated oil temp is when the operation has reach equilibrium and the oil itself If you assume that op temp is 100°c you will have that available on the PDS of hte oil. However it is usually a bit cooler and therefore will be thicker. If you know your exact operating oil temp it can be calclulated easy eough using the ciscosity calculator mentioned above.

 

[ZZman]

So 100 Celsius is equal to 212 Fahrenheit. Does this sound about what a normal engine oil temp might be?

If so than a 30 weight oil at this temp would be a certain thickness and a 50 weight would be a certain thickness. Is that right?

 

[BrianWC]

Originally Posted By: StevieC
If an Oil is a 5w30 then it's a 30wt oil when hot but pumps like a 5wt when cold. It's always a 30wt oil. You can get this information off the MFG's website. Look at the CST value. Most 30wt oils are 9cst when warmed to 100oC.

Hope this helps...


It's incorrect to say it pumps like a 5 weight when cold when you are comparing directly to a 30 weight. The "w" numbers should only be compared to each other.

 

[Bryanccfshr]

Yes.

This Chart is what you need to refer to. it is an "SAE J300 chart"
http://www.infineum.com/information/api-viscosity-2004.html

 

[moribundman]

Originally Posted By: Quattro Pete
Originally Posted By: ZZman
My question is: After a vehicle is warmed to operating temp what would the weight of oil be?

The weight doesn't change.


Don't you mean the oil's mass doesn't change?

 

[Quattro Pete]

LOL. I meant weight as in 'grade'.

 

[Jim Allen]

RE Oil Temps: It's pretty safe to say that most engine oil temps normally run at around 200 degrees,give or take, depending on the workload. I surmise that's why oil viscosity is rated at that approximate temperature. A hard working engine might run hotter, hence the need for a higher viscosity oil. Conversely, a short hopper, or low stress engine, may run at a lower temp and can safely use a lighter oil, or run with what may effectively be a higher viscosity oil at those lower temps. That may cover you for shearing and fuel dilution, which can reduce viscosity over time.

 

[Junior]

Originally Posted By: StevieC
Most 30wt oils are 9cst when warmed to 100oC.

Hope this helps...


10 to 11.
9.3 is the dividing point between 20 and 30

 

[moribundman]

Originally Posted By: Quattro Pete
LOL. I meant weight as in 'grade'.