Oil Case Studies

A novel sample environment to probe the surface structure of engine oils

Organic Friction Modifiers (OFMs) are surfactants included in engine oil formulations. They adsorb on metal surfaces, forming compact surface layers that act as protective coatings to reduce friction and wear occurring between mechanical engine parts.

The use of OFMs is associated with more energy-efficient engines and a reduction in CO₂ emissions. The design of effective new formulations and novel OFMs relies on a detailed understanding of how OFMs self-assemble at interfaces and how their surface structure changes with tribological conditions.

Protecting the environment whilst maintaining efficient engine performance

Poor air quality and reduced greenhouse gas emissions are at the forefront of public discussion, as well as being high on the agenda of worldwide policy makers. Many industries are embracing rapid changes in response, as is especially visible in the automotive sector, with the introduction of technologies such as gasoline particulate filters (GPFs). GPFs are positioned in a vehicle’s exhaust system and filter fine particulate matter (PM) produced by the engine. Recent legislation in places such as China, India and Europe will drive the adoption of GPFs on the majority of new gasoline, and hybrid electric, vehicles.

Whilst GPFs benefit public health and the environment by filtering out PM, they can also become gradually blocked by collected material. Captured carbonaceous particles (e.g. soot) can routinely oxidize away; however, inorganic PM (e.g. ash) typically remains in the filter for life, slowly blocking it and potentially reducing the fuel economy and power of the vehicle. Inorganic PM is predominantly derived from engine oil additive chemistry, which plays an important role in improving fuel economy, performance, and engine lifetime.

Mimicking Diesel Soot to Reduce Engine Wear

Fuel combustion in diesel engines leads to the production of nitrogen oxides (NO_x) which are harmful to the environment. Retarding the fuel injection timing and recirculating the exhaust gas back into the engine reduces overall NO_x emissions, however, this can also lead to the formation of diesel soot particles within the engine oil. Excessive build up of soot in engine oil accelerates engine wear, ultimately leading to lower fuel efficiency and premature engine failure.

Reducing wear and tear with effective lubricants

Effective lubrication has a significant impact on a number of applications ranging from human artificial joint implants to energy efficiency of internal combustion engines and the reliability of offshore wind turbine gearboxes. At low running speeds and high contact pressures the fluid film cannot be maintained and therefore effective lubrication is greatly influenced by the presence of chemical additives in the lubricant. These additives interact with the lubricated surfaces to form nanoscale tribofilms that reduce both material wear and energy losses due to friction. Understanding the mechanisms by which these tribofilms form is essential for development and optimisation of the next generation environmentally friendly effective lubricants, materials and tribological systems.

Controlling crystallisation in fuels and biofuels

The “freezing” of diesel fuel in winter has been a problem since its inception. Wax crystals nucleate and grow and block fuel lines and filters which can lead to vehicle failures and motorists being stranded. Additives are used to control these crystals but, over recent years, the use of biofuels (fatty acid methyl esters) within diesel blends has become increasingly common.  This can adversely affect the low temperature operability of the fuel. Legislation demands that biofuels are part of diesel blends throughout the EU, with levels expected to increase.

Enhancing oil recovery

Water injection in a well known method used to increase oil recovery. Until around 2000, mechanisms behind this were believed to be physical (maintaining reservoir pressure) in nature. Through the development of BP’s LoSal® (reduced salinity) enhanced oil recovery (EOR) technology, modification of the brine chemistry of the injection fluid has been shown to play an important role in oil recovery performance.