Confusing Different Grade of engine oil

[Lufu]

I notice engine oil comes in different grade, 15W50, 20W50, 5W40 etc..

how to i decode it? what does the 15 means? W50 means ?

 

Which is better than another ?

 

Thanks to all the experts :-)

[Wrxblue]

Please note that we are using the

 

SAE Viscosity Grade

 

Viscosity is a measure of an oil's flow characteristics, or thickness, at certain temperatures.

 

The low-temperature viscosity (the first number, 5W in the example above) indicates how quickly an engine will crank at cold temperature and how well the oil will flow to lubricate critical engine parts at low temperature. The lower the number the more easily the engine will start in cold weather.

 

The high-temperature viscosity (the second number, 30 in the example above) provides thickness, or body, for good lubrication at operating temperatures.

 

A multigrade oil (for example, SAE 5W-30) provides good flow capability for cold weather but still retains thickness for high-temperature lubrication.

 

so depending on your location and usage the above should give you a guide on the type of oil you should use.