Quote:
Originally Posted by Flarpswitch
Before synthetic oil, I used to use Castrol almost exclusively because it was more resistant to shear. At least I bought into the sales pitch and the hype. What I know about synthetic oils is that they are very resistant to shearing and provide reliable lubrication for longer intervals under high load. Something about all the molecules being more uniform in size (smaller) and having stronger bonds. I heard that from someone who claims that he is not on the payroll for the company that makes that claim. I still trust what he says in spite of the fact that he does get free stuff on occasion.
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Synthetic is generally more resistant to shear in most, but not all cases. However, even the most advanced synthetic that most users will be willing to pay for will shear out of, or close to our of grade. Meaning if you run a synthetic rated as api sp or acea a1/a5 10w, 5w or 0w30 it will shear to a 20 grade or a hths of about 2.6cst. If you want to shoot for 3.04 as the example above you’ll want an api 5w or 0w40 or acea a3/b4 or c3. These will start out at 3.5cst HTHS or there about and shear down to just above 3.04. For reference peruse all the uoas the internet has to offer.