Our resident ester developer
Tom NJ may want to expound/expand on this amazing lubricant.
You nailed it Mola. Just a few more details for those interested in these products.
The MIL-PRF-23699 specification was developed by the US Navy nearly 60 years ago and was last updated in 2014. It controls most of the jet turbine oil used by the US military and most foreign militaries as well. The Air Force also developed a specification known as MIL-PRF-7808 in the early 50s, then based on a diester but later updated to polyol esters like 23699.
The main difference between the Navy 23699 and the Air Force 7808 specifications is viscosity; the Navy spec is 5 cSt @ 100°C and must be pumpable at -40°C while the AF spec is 3 cSt @ 100°C and must be pumpable at -51°C. The reason for the better low temperature requirements of the AF spec is that some AF bases are located in cold Arctic regions while Navy bases are near water. (In fact the AF bases do not actually get to -60°C and the fuel will not function at those temperatures anyhow.)
The AS5780 specification was developed by the commercial airline industry through the SAE E-34 Propulsion Lubricants Committee to address the more severe requirements and liability in commercial jets. Military aircraft undergo frequent maintenance including oil changes while commercial jets often have OCIs of six plus years (but does turn over from frequent top offs). Deposits are a major concern in commercial jet engines, which is why additional high temperature deposit tests were added to the AS5780 spec like the HLPS and vapor phase coking tests.
The most common POEs used in these oils are pentaerythritol esters fully esterified with fatty acids ranging from five to 10 carbons in chain length. Shorter acids introduce problems with volatility and odors while longer acids are detrimental to low temperature flow and coking propensity. Other types of POEs may also be used, such as a blend of TMP and Dipentaerythritol esters.
Several different levels of jet oil performance exist, which are commonly referred to in the commercial industry as “generations”. The current highest quality oils with the lowest coking propensity are called “4th Generation” oils, and are increasingly in demand by commercial airlines due to the cleaner operation and reduced maintenance they provide. Some examples of 4th Generation oils are Eastman's Turbo Oil 2197, ExxonMobil's Mobil Jet Oil 387, and Shell's Ascender.
More formally, the specifications also break out performance levels based on test results. The 23699 spec defines four classes of performance; STD (Standard), HTS (High Thermal Stability), C/I (Corrosion Inhibiting), and EE (Enhanced Ester). The AS5780 spec defines two classes; SPC (Standard Performance Capability) and HPC (High Performance Capability).
Meeting the military specifications is sufficient for approval by the NAVY or AF and subsequent sales. In the commercial arena, however, an AS5780 approval is just the first step and is followed by engine builder approvals and flight evaluations in a variety of engines. Full approvals needed for sales to airlines takes a good 10 years and costs millions of dollars, which is why there are so few players and technical advancements are slow. Over 90% of the commercial jet engine oil is supplied by just three companies, ExxonMobil, Eastman, and Shell.
The very same turbine engine oils sold into aviation applications are also sold for aero-derived turbine engines used in some ground based industrial installations, such as electrical generation power peaking turbines. Total global demand for synthetic jet turbine engine oils in all applications is in the neighborhood of 8-10 million gallons, compared to 2.2 billion gallons for PCMOs.
Speaking of PCMOs, NO you should not use jet turbine oils in your car! In addition to being very thin, jet oils have no detergents, no dispersants, no ZDDP, no EP additives, weak anti-rust, and excessive seal swell in car engine elastomers.
I’d be happy to answer any questions you may have on these unique oils.
productcatalog.eastman.com
productcatalog.eastman.com
