Lubrication Systems (1) Wet sump oil systems are most commonly used in gas turbine engines. (2) In most turbine engine oil tanks, a slight pressurization of the tank is desired to ensure a positive flow of oil. Regarding the above statements, a. both No. 1 and No. 2 are true. b. only No. 2 is true. c. neither No. 1 nor No. 2 is true.