OIL Temp Question, Your thoughts

[Gary Allan]

Jake:

Things may have changed in the past 25 years with oils (yes, I'm sure they have)...but the last time I was taught this stuff (I'm here for a refresher course) ..there is no "variable visc" oil. Sure the stuff changes in viscosity with the temp ..but ..it's not "inversely reactive". They're all thinner when hot and they're all thicker when cold.

Here's what I was taught through an SAE/API course:

10w-30

meets the MAX requirments of 10 weight oil

it IS 20 weight oil

meets the MIN requirements of 30 weight oil

10w-40

meets the MAX requirements of 10 weight oil

it IS a 30w oil

meets MIN requirements of 40 weight oil

anything with a "w" is a winter grade that (I believe) pours (flows?) at a specified temperature.

In the past the term multiviscosity just meant broader range. It's still one viscosity ..but has a broader index.

Can anyone update me for the newer generation of multiviscs? Where does a 15-50 fit in that rational (35 weight?) ...and how in the heck do you describe Mobil 1 0w-30? A 20 (15 maybe?) weight oil that EXCEEDS ALL SPECS BELOW 5w?

 

[jjbula]

quote:

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Originally posted by jake:
question? say a oil is 10wt. at 40c.,on start up. - and 30wt.at 100c. one of my trucks runs 170-180deg. water, checked with 2 mech. gages.QUESTION? is----- if oil doe's not reach full temp. 100c. say-- is oil only 20wy. ect. ??? just a thought ....thank's

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Jake,

When you see this on a tech sheet:

Viscosity 40°C Cst (ASTM D-445) 61.00

Viscosity 100°C Cst (ASTM D-445) 10.00

It's telling you that as the oil heats up from 40c to 100c the viscosity decreases from 61 to 10. Some data sheets even have this info:

High Temperature/High Shear Viscosity

302°F/150°C cP 3.2

Cold Cranking Viscosity

@ -30° C, cP 6,000

If you oil got to 150C it would be down to 3.2 cP.

Cheers

 

[widman]

The oil temp reading is very dependent on where it is measured, and of course driving conditions. And it can take a long time to get there, depending on load, air temp, and sump capacity. The power plants I service have to start the engines 1 hour before going on line to let them get up to temp before putting a load on them. Of course they have a 140 gallon sump.

 

[jake]

thank's to all, for the info.
jake.