Petrochemical additives refer to a wide range of chemical substances that are added to petroleum-based products or derived from petroleum to enhance their performance or modify their properties. There are various types of petrochemical additives used in different industries and applications. Some common types include:

1. Antioxidants: These additives help prevent oxidation and degradation of petroleum products, such as fuels and lubricants, by inhibiting the formation of harmful free radicals.
2. Antifoaming agents: These additives are used to reduce or eliminate foam formation in petroleum-based products, such as oils, solvents, and coolants.
3. Detergents and dispersants: These additives are added to fuels and lubricants to keep engines and machinery clean by preventing the formation of deposits, sludge, and varnish.
4. Viscosity modifiers: These additives are used to control the viscosity or flow characteristics of petroleum-based products, such as lubricating oils, greases, and hydraulic fluids.
5. Corrosion inhibitors: These additives help protect metal surfaces from corrosion when they come into contact with petroleum products, such as fuels, oils, and coolants.
6. Octane enhancers: These additives are used to improve the octane rating of gasoline, which helps to prevent engine knocking and improve fuel efficiency.
7. Demulsifiers: These additives aid in the separation of water from petroleum-based products, such as crude oil or emulsified fuels.
8. Colorants: These additives are used to add color or tint to petroleum-based products for identification or aesthetic purposes.

These are just a few examples of the types of petrochemical additives available. The selection and use of additives depend on the specific application and the desired properties of the final product.