Oil thicknes chart

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Feb 9, 2004
Just wondering, in real life terms, when you see an oil thats lets say a 20w50, and the Cst @ 100c is 17 and another is 19, is that a great real life difference?
Looks like the 19 cSt would be about 12% thicker than the 17. I'd say that is significant. You might see a slight increase in oil pressure. My pressure went from 36 to 45 going from a 10.5 cSt (5w30) to a 13.5 cSt (10w40), but that is about a 29 percent increase.
Just ever so slightly... For eg. Castrol Syntec 5-50 SJ formula had a Cst at 100C of 19.5. The SL formula is 17.5. There is a very tiny seat-of-the-pants difference (especially if used back-to-back), but not really anything to write home about.
The Cst is at 100c. If it were at 101c you might be at 16. It doesn't matter whatthe specs say, they are all an average of what was tested. The bottles you buy could be anywhere from 15-20 who knows. I spoke with a rep at a refinery about this and he said the numbers they post are only samples taken. It can very greatly by a 1 degree change in temperature.
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