technically it's slang.
dope is a somewhat generic term for "stuff" (noun). Since oil is "stuff", i guess it qualifies as dope....
When I worked in a computer factory in the 70s the shop workers had 4 separate meanings for the word "pookie":
1) silicon heat xfer compound or heatsink pookie;
2) CRT yoke magnet rubber cement (aka gorilla snot) or magnet pookie;
3) a 2 part epoxy adhesive or Devcon pookie;
4) silicone RTV/potting compound or potting pookie.
In other words, if it was too cumbersome to say in casual conversation, it was "pookie". Dope has the same roots.