Be aware, that some smoke generators use Oil, and some use a glycol mixture which is not oil at all.
X-craft was using the Mack smoke generators in his German Z boat.
http://www.rcuniverse.com/forum/m_16...tm.htm#1735617
Also see:
http://www.rcgroups.com/forums/showthread.php?t=385672
http://www.rcgroups.com/forums/showthread.php?t=330647