Lubricants and GDI Engines A Complex Relationship

Lubricants and GDI Engines A Complex Relationship

Mar 18, 2016

Topics: Passenger Cars

Within the past several years, gasoline direct injection (GDI) technology has had a beneficial impact on the passenger car market–OEMs have chosen this technology as a means by which they’ll achieve increasingly strict fuel economy goals.

GDI is smart technology for this purpose: smaller GDI engines generate more power and can directly impact fuel economy targets. Industry experts anticipate that by 2020, approximately 39 percent of all cars produced globally will utilize GDI engines.

In order for GDI engines to reach their full potential, the right lubricants are required. That means advanced additive technology, comprehensive testing and new considerations in the face of pressing challenges associated with GDI engines. Developers of the proposed GF-6 specification have accounted for these new challenges, incorporating new tests that will help ensure modern hardware is best enabled to provide heightened efficiency.

Why GDI now?

GDI technology has existed for many years, but only recently have OEMs begun to take advantage of the ways in which the technology can help provide better fuel economy for passenger cars.

Simply, GDI hardware allows for engine downsizing, or utilizing smaller engines to produce the same amount of power and torque as larger port fuel injected (PFI) engines. To accomplish those greater power and compression ratios, GDI engines operate by spraying fuel directly into the engine cylinder, providing a cooling effect. The cooling effect allows the engine to produce increased compression ratios and more torque, resulting in greater fuel efficiency. GDI engines can also incorporate turbocharger technology (TGDI), which recovers energy that is otherwise lost through exhaust systems to further increase fuel efficiency.

For instance, a 4-cylinder GDI engine can generate the same levels of torque as a 6-cylinder PFI engine. Four cylinders produce less friction and maintain more energy than six cylinders, directly contributing to better fuel economy.

The implication for lubricants

While downsizing is a reliable path to reaching fuel economy goals, downsized engines run under more extreme conditions than traditional engines–and that requires heightened durability and protection from lubricants.

GDI and TGDI engines rely on increased cylinder pressure, slower operating speeds and hotter temperatures to generate the power that allows them to operate more efficiently than PFI engines. However, due to these more severe operating conditions, there is concern over the following:

  • Greater potential for oil oxidation, compromising the oil’s protection against wear
  • Greater potential for fuel to mix with the lubricant, thereby increasing the potential for higher levels of acid and sludge
  • Greater likelihood of increased oil consumption within the engine, leading to a shorter drain interval

For these three reasons, shear stability–the measure of a lubricant’s ability to maintain its original viscosity and characteristics under potentially severe conditions–is very important in modern lubricants for GDI applications. A higher shear stability means the lubricant can withstand GDI conditions without succumbing to oxidation, mixing and increased consumption. And it’s not the only new consideration that oil marketers and additives makers must take into account.

Additionally, oil marketers must approach formulating for GDI engines at a time when lubrication viscosities are trending lower and lower. Like GDI engines, lower viscosities have come to greater prominence for their positive effects on fuel economy. Thinner oils provide less resistance as they are moved throughout an engine, resulting in less energy loss and greater fuel economy. Offering the necessary protection and durability for modern engine technology in a low-viscosity lubricant requires the right additive technology.

Formulating for success

The industry has recognized the impact that lubricants can have as OEMs move toward using new technologies to meet fuel economy goals. Oils formulated with additive chemistry that can help prevent LSPI and accelerated chain wear can successfully enable the full potential of GDI and TGDI engine hardware. This means achieving maximum fuel economy and peak reliability for the end user.

Lubrizol Additives has played a critical role in developing the new engine tests incorporated within the proposed GF-6 specification. Through its involvement in this process, Lubrizol has forged a deep understanding of the ways in which additive technology can be leveraged to prevent the challenges associated with GDI engines. Beyond GF-6, Lubrizol has developed and is continually testing experimental additive chemistry in specially formulated oils in order to gain insight into the challenges of GDI engines.

Lubrizol’s unmatched testing capabilities and expertise allow for unique and specific insight into these challenges and how they can be overcome.

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