STP may refer to:
STP (motor oil company)
STP is an American brand and trade name for the automotive additives, lubricants and performance division of Armored AutoGroup which also own the brand Armor All which was acquired by Spectrum Brands.
Douglas Harper's Etymology Dictionary
commercial motor oil additive, probably an initialism (acronym) of scientifically treated petroleum. As the street name of a type of psychedelic drug, attested from 1967.