This paper presents the experimental results on the behaviour of creeping discharges at the vegetable or mineral oil/solid insulator interface under positive and negative DC voltages. Palm fatty acid ester (PFAE) oil and crude rapeseed (CRS) oil are used as the test vegetable oils. A solid insulator is the oil impregnated high density pressboard with and without a grounded back side electrode (thin copper rod) and brass counter electrode. The tungsten needle electrode (high voltage electrode) is placed on the pressboard surface to generate the creeping discharge. The discharge shape, streamer extension, discharge current, emitted light signal and oil or pressboard breakdown voltage are examined in the vegetable and mineral oils. The behaviour of DC creeping discharge is largely different from that of AC or impulse creeping discharges, because of a significant difference between the DC and AC (or impulse) on the electric field strength which is applied to the pressboard and oil.