BrianOk:
This is in form of a precaution and advice:
Don't just presume that there is one, generic Dowtherm or Mobiltherm heat transfer fluid. There are various formulations of each of these brandnames and the properties are not the same - otherwise, there would be only one substance. The reason there are various formulations is because there is a variety of different applications to which each one applies. From what I presume you need to know, I would advise you to call Dow or Mobil and discuss your needs with them directly - not on this forum. They are the experts in this field and the only ones who control the actual information regarding their products. I am certain that you will find them very cooperative in giving you the information that you require to apply their product.
I hope you succeed in getting what you need.
Art Montemayor
Spring, TX