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By now everyone has noticed and/or used an oil(s) with a multi-viscosity rating. With this post I'd like to take a little time to better explain the science and benefits behind this type of oil when compared against single grade oils.

If you already know this information, well then you've done your homework and may continue to the next post, for those who are lost at the mere mention of multi-viscosity then please continue on...

 

I do not intend on making this a long drawn out read, but rather to make it a little easier to understand without all the extra scientific terms no one wants to read. 

 

First we will start with the basics:

  • Single Grade(straight-weight): An oil that does not change viscosity within its given operating temperature range. "The 11 viscosity grades are 0W, 5W, 10W, 15W, 20W, 25W, 20, 30, 40, 50, and 60. These numbers are often referred to as the "weight" of a motor oil, and single-grade motor oils are often called "straight-weight" oils." -pulled from the "motor Oil" Wiki page
  • Multi--Viscosity: An oil that has the ability to change viscosity when exposed to different temperatures within a given operating temperature range. (eg. 0W-30, 5W-20, 5W-30, 10W-30, 10W-40, 15W-40, 20W-50) "The 11 viscosity grades are 0W, 5W, 10W, 15W, 20W, 25W, 20, 30, 40, 50, and 60. These numbers are often referred to as the "weight" of a motor oil, and single-grade motor oils are often called "straight-weight" oils." -pulled from the "Motor Oil' Wiki page.
  • The "W":: The "W" appended to any number in the weight of an oil stands for "winter" meaning cold-start viscosity to make engine starting in colder temperatures easier.

 

Now for the fun stuff. 

  • Single Grade: These oils maintain their weight throughout their operating temperature range.
  • Multi-Viscosity: Most people tend to think that multi-viscosity oils operate like table syrup, where cold syrup is thick and viscous and hot syrup is thin and much less viscous, however this isn't true of multi-viscosity oils. In fact, it is quite the opposite, when these oils are at ambient temperatures they are thin, this is where the first number in the grade of the oil comes into play, and easily moved about the engine which aids in start-up at low temps. however when the oil reaches its designated operating temperature(designated by SAE as 100ºC) it becomes thick and more viscous, this is where the second grade of the oil comes into play, aiding in coating and lubricating internal engine parts. 
  • Gear, axle, and manual transmission oils are rated on a separate SAE viscosity rating system, SAE J306, and should not be confused with engine oil viscosity, because the higher weight rating of these oils doesn't necessarily mean they are heavier in weight than their engine counter parts.

To wrap this up, i hope this has given you a little knowledge about the oil(s) you're using in your vehicle. And that you may take this knowledge and bestow it on those who are still learning. 

 

phuketJR

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Please try to keep tech and maint threads somewhat serious..it has been stated by admin that one goal to attract new members is a robust tech section. Thank you.

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