For the main objective the player only has to do two things. One of which is to shut down the oil pump. This is located at marker one up the stairs guarded by one guard and a few more along the way. The 2nd objective is a big target and somewhat easier. Destroy the big red oil tank. I suggest for the first go around to use air support etc and just destroy everything so you know the level. Of course it gets deeper then that for S-RANK and 100%...
100% Shutdown the Oil Transfer Pump .
100% Destroy the Oily Water separator tank.
100% Extract 4 child soldiers from Masa Village .
100% Exfiltrate the Hotzone before Mfinda Oil Field is sealed off.
100% Extract the Vulture from the Burnt down village.
100% Extract 4 walker gears.
1. Objective one is mandatory.
2. Objective two is mandatory.
3. Extracting the soldiers from the Masa village is somewhat easy enough. Bring a Sleep grenade or use Sleep Gas Dispersal when you SNEAK to the area in Masa Village where the 4 children are located. Remember do NOT set off the alarms or you will make them hostile.
4. To Exfiltrate the hotzone before it is blocked off you should place C-4 on the oily water separator pump. Explode it when you are completely out of the Hot Zone. The mission will end shortly. However note that this will ruin your opportunity to get 4 walker gears. So it must be ran a second time.
5. Extract the bird with a tranquilizing shot in the burnt village. See video it is just south west of Mfinda Oil Field.
6. Extract 4 walker gears. You can only do this after the pump and oil tanks have been exploded and shut down. After wards the walker gears will appear along the exit road. I suggest using a sleep grenade and taking them out then extracting each one. Make sure you have sleep grenades or even EMN mines.
:::: S-RANK ::::::
For the S-RANK. Bring along a rocket launcher for sure. You can go in blazing guns and get this one easily. Time is your factor here. See the video or read on.
Go to marker using a vehicle or the D-HORSE. Get out and head to the shut down the oil tank first. Try being sneaky here and infiltrate. Use a SILENCED weapon or better an SMG because there will be a few enemies. SMG fires faster and usually holds more rounds per magazine.
Once clear shutdown the pump. If you get caught run out of the facility. Head back to the top mountain as far as you can be away from the facility while still being able to see the Red Oily tank. Blast it with a rocket so it blows up then exit the hot zone.
If you do NOT get caught you can do whatever you would like. I suggest using C-4. Then escaping the area finally leaving the hot zone afterwards. Congrats !