Engine cleanliness is critical to the operation of a vehicle. Industry standards used to certify lubricating engine oils include rigorous checks on deposits in critical engine parts.
In recent years, the changes in engine design to meet legislation and changing user needs has altered the landscape of hot parts within the engine and introduced new ones such as those within turbo chargers. Tests have been introduced to reflect these changes, such as TEOST 33C, which is a screener evaluating oils in terms of turbocharger deposits. TEOST 33C is now an important industry test for certain lubricating engine oils.
One known source of deposits is the breakdown of the lubricating engine oil when exposed to hot engine parts. In this paper we describe our work using the TEOST 33C test to study the effects of different engine oil formulation components on deposit formation. We have looked at base oils, additive packages and solvency agents, but particular emphasis has been placed on viscosity modifiers.