A Better Blend

| April 07, 2005

EGR engines allow exhaust to flow from the exhaust manifold through a heat exchanger full of engine coolant, and into the intake air stream. This reduces nitrogen-oxide emissions, but also puts more stress on the engine oil.

For truckers running emissions-friendly EGR (exhaust gas recirculation) engines, new CI-4 oils are required protection. And for those running earlier designs, the super oil could offer great news when it comes to maintenance intervals.

Recycled exhaust gases in the combustion chamber create a hostile environment inside the engines. And since the oil’s job is to protect the engine from its own internal evils, a more hostile environment means a need for better oil – hence the new API (American Petroleum Institute) CI-4 designation.

Using EGR technology, engines ingest not only intake air (which is normally only about 100 degrees Fahrenheit), but also 30 percent of their own exhaust at temperatures well above 200 degrees. As a result, the oil itself gets hotter even though the engine’s coolant does not.

According to Kevin Harrington, commercial vehicle lubricants product advisor at ExxonMobil, “EGR engines can be expected to run as much as 25 to 40 degrees hotter than non-EGR engines. This could cause premature oxidation in non-robust oil formulations.”
Acid is another concern. That’s because the exhaust gas that re-enters the engine contains components that, in the presence of water vapor, can form strong acids. Left unchecked, these acids can rapidly degrade oil and attack the metallic components of the engine.

Soot is still another factor. As Peter Thomson, global brand manager for the ChevronTexaco Delo product line says, “The oil must have better soot handling capacity to deal with increased soot loads to prevent excessive wear.”

While engines won’t actually generate any more soot (and exhaust particulate must not rise according to the Environmental Protection Agency standard), more soot may actually enter the oil. That’s because the exhaust in the cylinder will reduce the concentration of oxygen, and this can make it take longer for soot to burn off, allowing it to reach the cylinder liner and rings, and work its way down into the oil. If soot isn’t kept in suspension, it increases the viscosity of the oil, interfering with proper lubrication. High soot levels can also result in abrasive wear on rubbing parts like valve train rockers.

Just what’s better?
The new CI-4 lube is a perfect example of how the pressure of regulations results in significant technological developments. “The CI-4 specification has several significant performance upgrades that were needed to help ensure that the new exhaust gas recirculation diesel engines operate at maximum performance,” says Dan Arcy, products marketing manager for Shell Lubricants. “These upgrades include improved wear protection to better combat the harsher operating conditions that are sure to develop in EGR engines.

“[One] result is improved soot handling capability. The oil’s ability to resist oxidation
(high temperature) has also been increased. The alkaline reserve (TBN-”total base number”) or ability to neutralize acids was improved because EGR engines generate more acids. And the volatility of the oil was reduced to improve deposit control and oil consumption.”

The jug for Chevron Delo 400 will look very much the same. But when the jug lists the CI-4 designation on the label, you can be certain you’re getting engine oil that incorporates some impressive improvements in engine protection.

According to ChevronTexaco’s Thomson, the API CI-4 oil must have better thermal stability to deal with higher operating temperatures. Many oil formulators are now using highly refined base stocks and higher levels of oxidation inhibitor additive.

Harrington of ExxonMobil says, “Due to the stringent requirements of API CI-4, oils must be formulated with higher quality Group I and Group II base fluids, as well as more robust additive systems than their predecessors.”

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