Krillitane oil

Krillitane oil was a substance used by the Krillitane race.

Functions
The oil's effects on other races were impressive, as it seemed to act as a 'lubricating agent' for the human brain, accelerating thought processes and increasing intelligence by a significant factor. The effects of the oil were only temporary, and soon after being ingested, the effects wore off. It would appear that Krillitane oil was not unpalatable, as the method of delivery was frying chips in it. No one who ate the chips, except for the Tenth Doctor, complained about their taste, and others, such as Rose Tyler, even complimented the chips' flavour.

History
Some time prior to 1140, the oil had become toxic to the Krillitane race, due to the race's frequent physiological and chemical changes. (NSA: The Krillitane Storm)

Krillitane oil was instrumental to the Krillitane in their plan to crack the Skasis Paradigm, using its effects to enhance the minds of the entire Deffry Vale High School, and then using technology to harness the collective consciousness of the students to work in tandem.

Several barrels of the oil were blown up by K9, covering the Krillitanes in it and subsequently killing them. (DW: School Reunion)