The last major step of the refining process is blending various streams into finished petroleum products. The various grades of motor fuels are blends of different streams or “fractions” such as reformate, alkylate, catalytically cracked gasoline, etc. Refineries blend compounds obtained either from their internal refining process operations as noted above, or externally, to make gasoline that meets specifications for acceptable motor vehicle performance. A typical refinery may produce as many as 8 to 15 different streams of hydrocarbons that they then must mix into motor fuels. Refiners might also mix in additives like octane enhancers, metal deactivators, anti-oxidants, anti-knock agents, rust inhibitors, or detergents into their hydrocarbon streams. Blending can take place at the refinery along the pipelines and tanks that house processed fuel or even at off-site locations or on ships or terminals once the fuel has left the refinery gate.
