few questions about viscosity

[volvlo]

hello
Im new here and I'm just trying to find the truth about the how the bloody oil engine works

I read alot of articles , watched tons of videos and the last was the bob oil guy uni but I still cannot make it clear ,I hope I can find the answers for my questions

1) the viscosity on engine oil is measured by SAE right so but i found that here bob uses the thickness instead of viscosity and the thickness I think is measured br Sc so 10 thickness is the perfect thickness for engine on operating temp , so whats the different between the viscosity and the thickness and which one should we look at

2) again why sometimes we have two oils lets say 10w30 and 10w40 in this case for cold temp before the engine starts the oil should be on 10 viscosity right and here we have the same viscosity for winter right , but we may find out that they have different thickness ??

3)lets say my vehicle likes 10w30 so when its winter Id use 0w30 and when its summer Id use 10w30 but isnt always the lower viscosity on W always better since it has lower thickness and better flow why dont ppl use such as 0w20 or 0w30 all the year even on hot weather

4) again lets say i live in cold area where my vehicle wants 0w20 why its recommended to use 0 or 10 w30 when its hot isn't the 20 is always 20 coz its at 212F which it doesn't matter the weather right

alots of questions but I still cant find out the real answer about the viscosity I hope some one can help me or provide some links to find my answers

last but not least when buying an oil it doesn't matter even if i buy the cheapest non brand oil since it meets the API lest say SN so its ok right

thank you

 

[bvance554]

The link that you want is your owners manual. Use the grade of oil that it recommends. Yes, brand of oil doesn't matter. Just make sure the appropriate certifications or approvals are on the bottle.

 

[userfriendly]

volvlo;
I think the SAE grading system is obsolete and causes confusion. You need 2 pieces of information;
The coldest temperature your engine will experience, and the HTHS requirement of your engine.

 

[FCD]

Disregard the Motor oil 101 section of the page, it's very biased and one sided.
The 10 refers to the centistokes of the oil at 100c , this would translate into a 30 grade oil.

 

[The motor guy]

It's actually quite simple. A 10w30 will have the thickness of a straight sae 10 weight when cold which is still going to be thicker than the straight 30 weight at operating temperature. Now a cold 10 weight is still thicker than a 30 weight when hot it's still way thinner than what a straight 30 weight would be when cold.

Remember the 10 in 10w30 thirty is the thickness when cold and the second number is the thickness at operating temperature.

 

[kschachn]

Originally Posted By: motor_oil_madman
It's actually quite simple. A 10w30 will have the thickness of a straight sae 10 weight when cold which is still going to be thicker than the straight 30 weight at operating temperature. Now a cold 10 weight is still thicker than a 30 weight when hot it's still way thinner than what a straight 30 weight would be when cold.

Remember the 10 in 10w30 thirty is the thickness when cold and the second number is the thickness at operating temperature.


No, it meets the J300 cold-cranking viscosity requirements specified for 10W. There is no SAE 10 oil.

 

[FCD]

Originally Posted By: kschachn
Originally Posted By: motor_oil_madman
It's actually quite simple. A 10w30 will have the thickness of a straight sae 10 weight when cold which is still going to be thicker than the straight 30 weight at operating temperature. Now a cold 10 weight is still thicker than a 30 weight when hot it's still way thinner than what a straight 30 weight would be when cold.

Remember the 10 in 10w30 thirty is the thickness when cold and the second number is the thickness at operating temperature.


No, it meets the cold-cranking viscosity requirements specified for 10W.

And there is no SAE 10 oil.

Exactly, the lowest SAE grade is 16

 

[aquariuscsm]

What confuses most people about multi vis is they think it starts out as a 10 and thickens up to a 30 when it gets hot. All oils thin out once they're hot.

 

[supton]

Originally Posted By: kschachn
Originally Posted By: motor_oil_madman
It's actually quite simple. A 10w30 will have the thickness of a straight sae 10 weight when cold which is still going to be thicker than the straight 30 weight at operating temperature. Now a cold 10 weight is still thicker than a 30 weight when hot it's still way thinner than what a straight 30 weight would be when cold.

Remember the 10 in 10w30 thirty is the thickness when cold and the second number is the thickness at operating temperature.


No, it meets the J300 cold-cranking viscosity requirements specified for 10W. There is no SAE 10 oil.


It's so tempting to think that 10W30 starts out as a 10 weight, and when warm it would be a 30. It'd be easier that way!

Found this chart.


The winter weight uses cP for viscosity at cold (and note how the test temperature changes!) while the second number uses cSt for viscosity at a fixed temperature--or in other words, completely differently measured for the two ends of the "rating" given to the oil.

Maximum cranking viscosity :
Quote:
This test method covers the laboratory determination of apparent viscosity of engine oils at temperatures between –5 and -35C and at high shear rates. The results are related to engine cranking characteristics of engine oil. A measured amount of sample is subjected to an extreme low temperature for 3 minutes. The rotor spins for 1 minute in the sample and the speed of the rotor is measured by keeping ohms resistance at zero. The speed-reading is used to determine the viscosity on a calibration curve.

The cold cranking simulator (CCS), ASTM D5293, correlates with engine cranking speed at low temperatures.


Cold cranking viscosity simulates the viscosity of an oil in crankshaft bearings during cold temperature start up.


From another link here :
Quote:
Kinematic Viscosity (ASTM D445/ISO3105): 1 centi-Stoke (cSt) = 1 mm2/s.

Absolute Viscosity is a measure of a fluid's internal resistance to flow and may be thought of as a measure of fluid friction and of the oil's film strength to support a load.

Dynamic or Absolute Viscosity: 1 milliPascal second (mPa·s) = 1 centi-Poise (cP)

High-temperature high-shear-rate (HTHS) viscosity is an indicator of an engine oil's resistance to flow in the narrow confines between fast moving parts in fully warmed up engines. The most common test for this is ASTM D 4683 as it closely mimics the conditions found in an engine's crankshaft and connecting rod journal bearings, as well as other narrow regions such as between the cam and follower on flat bucket tappets. This measurement influences such factors as fuel consumption, valve-train wear and bearing protection.

Cold cranking viscosity simulates the viscosity of an oil in crankshaft bearings during start up on a cold winter morning. The test determines if an engine can be cranked over fast enough to start under extreme cold ambient conditions. ASTM Method D 5293 simulates an oil's cranking resistance when cold, and thus indicates the lowest temperature at which an engine is likely to start.

Cold pumpability measures the resistance of an oil to pumping through the engine after a cold start. The most widely used test is ASTM D 4684. If an oil's viscosity becomes too high, pumping will be hindered with possible cavitation issues. Viscosity here becomes an important factor in determining whether the engine runs with sufficient lubrication after starting in severe cold conditions. The Cold Pumpability test is always conducted at 5°C colder than the Cold Cranking test to ensure the pump can deliver the oil to the bearings.

 

[53' Stude]

Supton: thank you very much for the chart and info

 

[TiredTrucker]

And also that viscosity is not "thickness". It is resistance to flow.