Which of the following additives is NOT typically used to improve the characteristics of lubricating oil?

The correct choice is an additive that is not typically used to enhance the characteristics of lubricating oil. Emulsion breakers are primarily used in the treatment of crude oil and water mixtures to separate the two phases, making them distinct from the additives that are commonly found in lubricating oils.

In lubricating oils, anti-oxidants are crucial because they inhibit oxidation, which can lead to the breakdown of the oil and formation of harmful sludge. This helps maintain the oil's integrity over time and ensures it can effectively lubricate engine parts.

Viscosity index improvers are used to enhance the viscosity of oil across a range of temperatures, ensuring that the oil remains effective in providing lubrication under varying operating conditions.

Detergent-dispersants serve to keep contaminants in suspension, preventing sludge and deposits from forming within the engine. This keeps the engine clean and functioning properly.

While each of the other additives plays a key role in ensuring the performance and longevity of lubricating oil, emulsion breakers do not have the same application or relevance in this context, as they are more associated with oil-water separation rather than lubrication enhancement.