As aircraft engines evolve, new technologies are employed to meet the demand for increased performance and efficiency.  But what about the oil that goes into these next generation engines?

Like the engines themselves, oil chemistry is changing to keep pace with more demanding  operational environments.  This puts the spotlight on the differences between Standard Performance Capable (SPC) Oil vs. High Performance Capable (HPC) Oil.  Here's what you need to know:

 SPC vs. HPC: What's The Difference?

Basically, the difference is stability.  High Performance Capable (HPC) oils are designed for higher thermal stability performance characteristics that are common with newer engines.  The engine manufacturers have made great strides in making turbine engines more fuel efficient, but these benefits typically come with increased operating temperatures.  These requirements have raised the bar with regard to thermal stability and engine oil life.

Standard Performance Capable (SPC) oils are still widely used in aviation.   Eastman Turbo Oil 2380 has been the gold standard for SPC oil in commercial aviation for many years.  However, as an SPC oil, it is designed for engines and accessories that do not demand the high thermal capabilities of an HPC oil.

There is even a difference in the oil used in APUs.  These oils are slightly thinner at 3 cSt (Centistokes), and offer much better low temperature performance properties to support engine starts and stops in colder environments.  This is essential for Extended-range Twin-engine Operations (ETOPS) when a cold start is required by the APU.

HPC Oil Benefits: What's In It For You?

Higher general operating temperatures aside, engine OEMs sometimes require lubrication system component inspections and cleanings as part of recommended best practice, but sometimes mandate attention to these components through Service Bulletins (SB) due to deposits or oil deterioration.  HPC oils have an inherent deposit-reducing characteristic.  This results in a cleaner operating engine and effectively reduces concerns regarding blockage of critical oil supply and scavenge tubes.  This reduction has allowed OEMs to rethink the time required between cleanings and/or inspections,  even reducing associated work-scope with such activities.  HPC oils have also proven to have a positive effect on internal component wear.  This is a direct impact on maintenance activity. 

Eastman has developed a Value Proven Tool that can quantify these potential maintenance savings that an operator can realize based on the type of engine they have should they utilize an HPC oil such as Eastman Turbo Oil 2197. 

A Cleaner Operating Engine With HPC Oil

Eastman Aviation Solutions has participated in and completed several studies that directly compare component health using both SPC and HPC oils.  These studies compared the health of critical components like oil vent tubes, bearings and oil supply tubes.  Overwhelmingly, HPC oils were found to deliver significant benefits such as lower levels of carbon deposits and a tangible reduction in tube blockage over extended time periods.  Bearing cleanliness was also found to be substantially improved though the use of HPC oils and their higher thermal stability characteristics.

Should I Be Testing My Oil System?

In general, oil quality and performance are typically maintained through normal consumption and top-off frequency (typically 0.1 quarts per operating hour).

However, this depends on your specific operational utilization level.  For example, oil testing is seldom employed in commercial airline operations.  This segment is classified as "high utilization" and as such, the aircraft engines consume sufficient HPC oil through normal operations and top-off.  In short, the oil in these engines is cycled though much faster than lower utilization segments.

Operators of business and general aviation aircraft and even turbine engine helicopters are typically considered "low utilization" and will still perform regular testing.  With lower utilization, these engines typically do not consume the level of engine oil that commercial operations do, and the original change of oil may remain in the engine for much longer periods of time without top-off.  These lower utilization segments also have an increased opportunity to accumulate moisture during periods of inactivity, all of which can accelerate the deterioration of the turbine oil.  

It's important to note that many modern engines have on-board systems to detect metallic wear chips in the oil system as well as accelerometers to detect vibration due to bearing deterioration.  These technologies alert operators to issues much faster than any oil sampling interval.

Where Can I Get More Information?

More information on HPC and SPC oil, the full line of Eastman Turbo Oils as well as other online resources such as the Eastman Value Proven Tool, are available at www.eastmanaviationsolutions.com.