Fundamental understanding about car oil

[Doug Hillary]

Hi,
keeganhmorgan - There are many interesting articles and Posts in the Science and Techonology Forums on here

The variances occur according the the lubricant's structure. For instance at 15C the viscosity of Castrol's 0W-40, Mobil Mobil 1 5W-50 and Mobil 3000X2 5W-40 the difference is minute. It is unlikely that any of these lubricants would be "better" (how do you judge that?) than another at that point. The same would apply to a bunch of SAE30 lubricants too of course

 

[keeganhmorgan]

True I guess it is hard to determine whether the oil is lubricating better. Would you recommend changing from a 0w and a 5w in different temperatures?

I guess it is now time for me to start doing some more research on oils before I start handing out information lol

 

[Doug Hillary]

Hi,
keeganhmorgan - Typically some engine makers suggest changing to a 0W-?? lubricant at temperatures below -25C or so. Others suggest a 0W=?? lubricant all year round - it is the designers call

At the Nurburgring 24hr last year many BMW engines used 0W-20 lubricants

 

[doitmyself]

Doug/keeganhmorgan,

It's time someone did a "sticky" to clear up the confusion.

Whenever I ask about the common idea that at "normal" starting temperatures, Gold Castrol 0W30 is "thicker" than most 5w30's , the responses are all over the place. It's counter intuitive to keeganhmoran's thinking that all 0Wxx perform better than 5Wxx at start up temps..

Again, this confusing topic comes up often and a "sticky" should be made to clear things up.

 

[jaj]

I think it's also necessary to distinguish between "lubricates" and "flows".

At start up there's no oil pressure and no flow; lubrication on the first spin of the crank relies on the chemical structure of the lubricant, not its viscosity.

 

[Doug Hillary]

Hi,
jaj & doitmyself - Thanks for contributing here - both BITOG "oldies" like me!

Many new BITOG Members Post in "an authoritative way" but sadly and obviously without a background of lubricant/lubrication experience/knowledge. This is to be expected as we all know - perhaps it is wise for the BITOG "oldies" to Post "corrective information" in a helpful manner - that way BITOG maintains its credibility

IMO we have an obligation to erradicate mis-information on BITOG whenever possible

I have been involved in this area for nearly 60 years and I'm still learning!