Green’s Dictionary of Slang

grease v.2

[grease n.1 (2b)]

(US drugs) to smoke opium.

[US]H. Leverage ‘Dict. Und.’ in Flynn’s mag. cited in Partridge DU (1949).
[US]Anslinger & Tompkins Traffic In Narcotics 309: grease. To use opium, especially to smoke opium.