AeroShell Oil Diesel 10W-40 is unique in being the only fully synthetic engine oil available in General Aviation. Features and Benefits AeroShell Oil Diesel 10W-40 is a fully synthetic, multigrade engine oil designed for use in the new generation of compression ignition (Diesel) Aviation Piston Engines. The formulation has been selected to be suitable in piston engines fuelled by Jet A or Jet A-1 and is designed for use in the latest highly rated turbocharged diesel engines under all operating conditions. AeroShell Oil Diesel 10W-40 MUST NOT be used in spark ignition, or Avgas powered aircraft engines