Synthetic sun roof paste is iffy. Castrol,s version is not a true synth, Mobil 1 sun roof paste is only a true synthetic if the date code starts with a 2, and the MB paste(not synthetic) warns that opening the sun roof when temperature is below -10 degrees F could damage the paste. If you have to open your sun roof when temp is below -10 degrees F, then a true synthetic should be used.
Hope this helped, Dan