Here's an online calculator that does some useful viscosity calculation.
http://www.geocities.com/CapeCanaveral/3655/VI.html
I didn't do a rigorous verification, but it agrees with some Mobil spec sheet values I pluged in.
http://www.geocities.com/CapeCanaveral/3655/VI.html
I didn't do a rigorous verification, but it agrees with some Mobil spec sheet values I pluged in.