When I worked on helicopter turboshaft engines (National Guard), there was this stuff I only remember as 1010 oil.
When the parts of the fuel system were to be "preserved" all fuel was drained and the fuel control an d lines were filled with this stuff. I only found one reference on the web.

http://www.bmpcoe.org/bestpractices/.../nadep_15.html

Jim in Chicagoland