Turbo Oil 25Formulated for the high-load-carrying demands of today’s helicopter transmission systems, Eastman Turbo Oil 25™ can reduce wear on critical parts, improving reliability and operation safety in transmissions and gearboxes.ility, you can see improved fluid life in your engine. ETO 2389 is the most widely used 3 cSt synthetic lubricant in aircraft APUs, so you won’t be the first to switch.