[aravindwarrier]

Pardon my noobish question, but I am curious to know What is Temperature units? If neither degrees C nor degrees F

[cyneverdie]

Originally Posted by cyneverdie

Tell me about it , wish there was a 15w50 oil available like in the USA where 15w50 mobil 1 extended protection IS being heavily pushed .

oops : was on an international call whilst posting , I meant mobil 1 extended performance

[Sankar]

Originally Posted by aravindwarrier

Pardon my noobish question, but I am curious to know What is Temperature units? If neither degrees C nor degrees F

Don't rack your brain with that phrase. It was used to explain the oil grades in layman's terms.


Engines are designed to operate at specific tolerances at certain specific temperatures. And the oil grades are determined to be used in a particular engine based on the tolerances of the internal components and also based on the optimum operating temperature that engine is designed to run at.

xW40 and xW50 have different viscosities or thickness when the engine is at the operating temperature. xW50 being more thick. Using a thicker oil in an engine designed to use xW40 range oil is not beneficial - unless the manufacturer recommends it under higher temperature operating conditions.

Being thicker the xW50 oil may not reach the places 'efficiently' in the engine which was designed to use a xW40 grade oil because the tolerances inside the engine might be too tight for a thicker oil even under optimum operating temperature of the engine.

When someone use a xW40 grade oil in an engine designed to take xW50 grade oil the tolerance between moving parts might be a bit too large for the less thicker xW40 oil to occupy and protect the moving parts. The big ends of almost all the engines are run on a oil film between the con rod and the bearing shells. The shear strength of the oil film and correct viscosity plays an important role in such situations.

Always use the correct grade of oil in the engines, when choosing the oil pay attention to the number that comes after 'W', at most of the places in India (except the colder regions up North) the number before 'W' can't be discounted. If a manufacturer recommends using a thicker grade for hotter climates use it.


And also the grading of xWx is not the same across all kinds of oil. For example gear oils if it says 90W then it's almost as thick as a 40W engine oil. This piece of information i found out yesterday as i was in a situation