Help request: Impact printer by the digital group

Hi all, I am in the process of restoring a 96 column impact printer sold by the digital group around 1977. (See my progress at: http://members.cox.net/oldcomp3/dgp/dgprinter.shtml) The first question I have is about the print head: Does anyone have any idea what, if anything, is the proper lubricant for a print head? What little lubricant I found on the heads felt like it might be a silicone grease of some kind. I have no idea if this was original lubricant or not. Labels I have found on other printers warn against oiling the print head, stating that the heads are lifetime oiled at time of manufacture. Next, I wonder if anyone on the list might have any information on the printer itself, which appears to have been manufactured by Practical Automation Inc., of Shelton Conn., or on the digital group electronics. Any ideas? -Bryan