Oil

Oil is a generic term for a slippery liquid that won't mix readily with water. Oils vary widely in composition but generally consist of mixed organic compounds.

Oils find frequent use as lubricants, fuels, and solvents. Transformers are among the users of oils in these capacities; however, they sometimes consume certain oily substances in larger quantities than strictly required, resulting in impairment of certain functions, disorientation, and temporary mental dysfunction. Though at first it may seem odd, some actively seek these seemingly-deleterious effects. What is odder yet is that humans seek out and consume varying solutions of a certain hydrocarbon with a single hydroxyl group and experience effects quite similar to those mentioned above. Further study is needed to explain this strange coincidence.

Fiction

Marvel Comics continuity

Head on down to Maccadam's Old Oil House for a pint.

Beast Wars II cartoon

Galvatron was a violent oilholic, constatly over-energizing and then rampaging.

From Teletraan I: The Transformers Wiki, a Wikia wiki.