[I]am way too shocked to learn what you guys speak of. CNG cylinder cleaning & draining oil from kit itself are 2 different thing.
to clean / test the cylinder it has to be removed from the vehicle and tested by authorised ENERCON shops. Plan and empty out cng and visit the shop, they will remove the empty cylinder from your vehicle, cylinder testing require 4 hours. 1st it is physically inspected for any fractures then it is tested for pressure.
all CNG stations have a warning banner from enercon for cylinder testing with the contact number of their shop in respective area. - Karachi one is on korangi road opposite CBM near national refinery gate.
Cylinder testing is mandatory every 5 years. [/I]