Vege. Prist would be used as a fuel additive in the Lear. Prist was also used in the Citation II P2-RDZ.
Prist was Ethylene Glycol Monomethyl Ether (EGMME), a carcinogenic. It now consists of diethylene glycol monomethyl ether (DEGMME). The primary purpose of this chemical is to prevent freezing of water in the fuel system of aircraft.
EGMME was the original additive used in jet fuel since the 1960’s when it was invented by the USAF and Phillips Petroleum. The military has been using the less hazardous and higher flash point DEGMME for over a decade now. In approximately 1994, the civilian ASTM specification was changed to DEGMME, as was the military specification to MIL-I-85470. Prist additive complies with the newer MIL-DTL-85470B specification. Both were and are mixed at .10 to .15% volume in Jet-A turbine fuel and aviation gasoline. DEGMME serves the exact same purpose of preventing icing of suspended water in jet fuel at altitude as did the previous EGMME product.
Prior to 1994, Prist additive specified ethylene glycol monomethyl ether (EGMME), certified as a pesticide with the EPA and Prist additive was advertised to retard growth of microbes in aviation fuels. The correct term is microbiostat, not microbiocide (-stat means it controls or retards growth, -cide means it kills microbes). With all of the new EPA requirements, it became economically prohibitive to certify the new DEGMME based additive as a pesticide. Summarizing the above, it is widely believed that DEGMME does have a retarding effect on microbial growth, however this is no longer an officially claim property for the Prist additive.
http://www.csdinc.org/prist/faq2.html#Q2
For non pressurised turbine aircraft operating at warmer ambient temps, a few liters of Avgas per week acts as a biocide and keeps the bugs at bay. At the Pratt's formula (of max 150 hours on Avgas per overhaul period) the effect on the engine would be negligable. But you didn't get that from me!!!
A trap for Cessna 208B Grand Caravan (PT6A-114A) operators: The US Flight Manual
mandates the use of Prist and prohibits the use of Avgas. This Cessna 208 Caravan's Australian Flight Manual which does not require Prist and permits the use of Avgas for 150 hours in the PT6A-114 engine. Same engine - different rules.