Oil grade vs engine temp

[Yannick]

Quick & easy one here ;

5w30 , 5 is the grade when oil is cold (thinner). 30 is the grade (thicker) when oil is hot.

Can we say when the engine temp gage(not the oil temp gage) is locate to its normal level when running the oil is now at 30grade? Engine temp gage is reading the prestone temp I think ,and not the engine (oil) temp. At then end when the engine get the 30grade oil ?
I hope you understand my question.
thanks

 

[Quattro Pete]

The coolant temp gauge is a dummy gauge on most cars these days. Besides, coolant temp is not always the same as oil temp. The oil is classified as "30 grade" based on one single measurement, which is done at exactly 100 degrees Celsius.

So, what is it really that you're trying to find out?

 

[Yannick]

So , Once the engine pass the 100degres C, the oil grade is now set to is thicker point (in the example, its 30) , true ? When engine get cooler, engine get thinner to the grade 5. correct?

 

[ARCOgraphite]

The oil is ALWAYS a 5w30 multigrade regardless of temp. Temp doesnt change the grade.

YOu want to know what the oil VISCOSITY is when the engine is warmed? Put a T-couple on the side of the pan or on the dipper.

The sump temp is likely lower than 100C during "normal" driving.

 

[Yannick]

Is the Oil viscosity thicker when engine is hot? (5w30). or viscosity never change is the oil property change ? I want to know what means 5 (cold) w 30 (hot) with simple explanation.

 

[EdwardC]

Oil is always thinner when hot.

A simple comparison between a 5W20 and 0W20:

At operating temp (~100C), both oils will have the same viscosity.

At cold temps, both oils will be thicker than at 100C, but the 5W will be thicker than the 0W.

 

[GenesisGuy70]

Originally Posted By: Quattro Pete
The coolant temp gauge is a dummy gauge on most cars these days.


Huh? Wouldn't that open up manufactures to liability? I always keep an eye on the coolant gauge and if it turned out that the engine overheated to the point of damage but the gauge never moved I wouldn't be very happy.

Though the Ford does have "safe mode".

 

[Whimsey]

Originally Posted By: Throt
Originally Posted By: Quattro Pete
The coolant temp gauge is a dummy gauge on most cars these days.


Huh? Wouldn't that open up manufactures to liability? I always keep an eye on the coolant gauge and if it turned out that the engine overheated to the point of damage but the gauge never moved I wouldn't be very happy.

Though the Ford does have "safe mode".


A dummy gauge will move to the center of the gauge and stay there within normal operating temps. If the coolant goes outside of this range then the gauge will rise to the danger zone and idiot light will come on and tell you you're scr*wed

.

Whimsey

 

[Nate1979]

Oil gets thinner was temperature increases. Oil gets thicker as it gets colder. So the oil cold will be thicker than the oil when it is hot.

 

[Pontual]

OK in easy terms: That 5w30 means that a 5 weight oil at room temperature, is so good that it will act like a 30 weight oil at 100C.
Ditto.

 

[GenesisGuy70]

Originally Posted By: Whimsey
Originally Posted By: Throt
Originally Posted By: Quattro Pete
The coolant temp gauge is a dummy gauge on most cars these days.


Huh? Wouldn't that open up manufactures to liability? I always keep an eye on the coolant gauge and if it turned out that the engine overheated to the point of damage but the gauge never moved I wouldn't be very happy.

Though the Ford does have "safe mode".


A dummy gauge will move to the center of the gauge and stay there within normal operating temps. If the coolant goes outside of this range then the gauge will rise to the danger zone and idiot light will come on and tell you you're scr*wed

.

Whimsey



Ahhhh gotcha. But if it the gauge moves in correlation to coolant temp doesn't that technically make it not a dummy gauge....? I'm just curious what is meant by "dummy".

 

[SwampSurvivor]

Originally Posted By: Throt
Originally Posted By: Whimsey
Originally Posted By: Throt
Originally Posted By: Quattro Pete
The coolant temp gauge is a dummy gauge on most cars these days.


Huh? Wouldn't that open up manufactures to liability? I always keep an eye on the coolant gauge and if it turned out that the engine overheated to the point of damage but the gauge never moved I wouldn't be very happy.

Though the Ford does have "safe mode".


A dummy gauge will move to the center of the gauge and stay there within normal operating temps. If the coolant goes outside of this range then the gauge will rise to the danger zone and idiot light will come on and tell you you're scr*wed

.

Whimsey



Ahhhh gotcha. But if it the gauge moves in correlation to coolant temp doesn't that technically make it not a dummy gauge....? I'm just curious what is meant by "dummy".


Dummy being that it doesn't correlate to any real temperature. Fords have had dummy coolant gauges forever, along with oil presssure.

 

[A_Harman]

Originally Posted By: Yannick
Is the Oil viscosity thicker when engine is hot? (5w30). or viscosity never change is the oil property change ? I want to know what means 5 (cold) w 30 (hot) with simple explanation.


The designation 5w30 means that the oil meets meets viscosity specifications defined by the Society of Automotive Engineers. There are two different viscosity classifications: low and high temperatures.

The "W" grades are for low temperature flow characteristics affecting properties during subfreezing temperatures. SAE grades for W oils are 0W, 5W, 10W, 15W, 20W and 25 W.

The high temperature grades are for oils meeting certain certain ranges of viscosity at 100C. SAE grades for high temperature are 16, 20, 30, 40, 50, and 60.

So a 5w30 oil is one that meets flow requirements that meet the 5W specification at subfreezing temperatures, and the 30 specification at 100C.

There are also single-grade (aka straight-grade or monograde) oils that meet only low or high temperature specifications. SAE 10W would be an oil for winter use only. SAE 30 would be for use only above freezing temperatures.

 

[4wheeldog]

Originally Posted By: Throt
Ahhhh gotcha. But if it the gauge moves in correlation to coolant temp doesn't that technically make it not a dummy gauge....? I'm just curious what is meant by "dummy".


Output from the sensor mounted on the engine is fed into the ECU, and the ECU sends the info it's software deems necessary to the dummy gauge. "Normal" operating temperature might be 50 degrees wide. Once that is exceeded, the gauge goes up....To another predetermined level. When it reachs "Too hot"......The dummy gauge pins itself. The movement of the gauge does not correlate to normal analogue type input.

 

[Michael_P]

On a Ford, the coolant temp is an inaccurate version of the real deal. The oil pressure gauge is a dummy gauge, but the temp gauge correlates actual engine temp. Just drive a Ford on a cold day, then on a hot day first start of the day. Also, if you ever had a pinhole in the radiator, you will see it gradually rise to "H" as the coolant diminishes. Besides, the sensor is a variable pot, not a switch.

 

[Whimsey]

Originally Posted By: Miller88


Dummy being that it doesn't correlate to any real temperature. Fords have had dummy coolant gauges forever, along with oil presssure.



Actually my 1989 F-150 with the 4.9 had Ford "semi" real gauges for the oil pressure and engine temp. Sad to say my 2002 F-150 4.6 has pure dummy gauges.

Whimsey

 

[Kuato]

Originally Posted By: Yannick
Is the Oil viscosity thicker when engine is hot? (5w30). or viscosity never change is the oil property change ? I want to know what means 5 (cold) w 30 (hot) with simple explanation.



In cold temperatures, the 5w30 behaves as a 5 weight oil would, to be a thinner consistency. At high temperatures, the 5w30 behaves like a 30 weight oil. There is much chemistry involved to make this happen but it is necessary since a 5weight oil at high temperatures would be too thin, and a 30 weight oil at very low temperatures would be much too thick.

Hopefully that helps.

 

[GenesisGuy70]

Originally Posted By: 4wheeldog
Originally Posted By: Throt
Ahhhh gotcha. But if it the gauge moves in correlation to coolant temp doesn't that technically make it not a dummy gauge....? I'm just curious what is meant by "dummy".


Output from the sensor mounted on the engine is fed into the ECU, and the ECU sends the info it's software deems necessary to the dummy gauge. "Normal" operating temperature might be 50 degrees wide. Once that is exceeded, the gauge goes up....To another predetermined level. When it reachs "Too hot"......The dummy gauge pins itself. The movement of the gauge does not correlate to normal analogue type input.


Gotcha. Learn something new everyday! I didn't know any of that. Thanks.

 

[Quattro Pete]

Originally Posted By: Throt
Gotcha. Learn something new everyday! I didn't know any of that. Thanks.

Yeah, in my 530i for example, the coolant temp gauge needle will sit dead at 12 o'clock position regardless if the actual coolant temp is 75 celsius or 115 celsius. That is called the "dead range." Supposedly car manufacturers were receiving too many inquiries from customers asking why the temp gauge keeps fluctuating, so the manufacturers decided to just keep it planted in one spot within some range of normal coolant temperatures. Only extreme departures from normal will make the gauge move one way or the other.

It prompted me to create this tongue-in-cheek diagram at one point...

 

[OVERKILL]

Originally Posted By: Yannick
Quick & easy one here ;

5w30 , 5 is the grade when oil is cold (thinner). 30 is the grade (thicker) when oil is hot.

Can we say when the engine temp gage(not the oil temp gage) is locate to its normal level when running the oil is now at 30grade? Engine temp gage is reading the prestone temp I think ,and not the engine (oil) temp. At then end when the engine get the 30grade oil ?
I hope you understand my question.
thanks


I'm just going to quote myself from another thread here where I believe I explained it quite well:

Missing are the new SAE 16 and 12 grades due to the date of the post.

Original discussion here:
https://bobistheoilguy.com/forums/ubbthreads.php/topics/3515622/Oil_change_question


The number in front of the W is not a representation of an SAE 5 "when cold", which doesn't exist as a motor oil grade, neither does a 10 or a 15, all of which are a xW classifications. The same goes for a 0. Is there an SAE 0? No. The SAE grading system for oils under the non-W classification starts at SAE 20.

Just as an example here, Mobil 1 0w-40 and Mobil 1 0w-20 both carry the 0w designation. Which means they meet the cold temperature performance requirements for that classification. This classification is simply a set of limits for MAXIMUM viscosity at -40C and -35C respectively. That is the ONLY thing those two oils have in common:

M1 0w-20:
Visc@100C: 8.7cSt
Visc@ 40C: 44.8cSt
MRV@ -40C: 9,200cP

M1 0w-40:
Visc@100C: 13.5cSt
Visc@ 40C: 75.0cSt
MRV@ -40C: 31,000cP


Is 9,200cP close to 31,000cP? Nope. But they are both under 60,000cP at -40C (and under 6,200cP for CCS @ -35C), so they both get to carry the 0w designation. There is no temperature that M1 0w-40 is even CLOSE to the same viscosity as the 0w-20.

You'll notice the 0W and 5W designations have the exact same visc minimums @ 100C, with no maximums for 100C or HTHS. You'll also notice the distinct absence of an SAE 5, 10 and 15 grade on the chart

Those grades only exist as ISO hydraulic oil grades, not engine oils.