<VV> Re: viscosity vs temp

[djtcz at comcast.net]

> 
> Anyone with a digital oil pressure gauge, using synthetic oil, can easily 
> verify that, indeed, the oil's viscosity index decreases (oil gets thicker) 
> as the oil cycles over its heat range. 
> Jim Davis 
> 
http://www.mpc-home.com/htmls/viscosity%20chart.jpg

If I understand the question right, I think the answer is >>not<< that synthetic gets thicker when hot, but rather that it does not thin out as much.
If, at 100C an oil's viscosity is ~15 cst it would be labelled 40 wt.  If at that temp it was ~11 cst it the label should be 30 wt.

At 40 C (not an SAE test temperature) they both would be over 100 cst.