On day 2 of the Big Oil job, complete the heist with the first engine being correct.
You will have to complete day 1 of the Big Oil job to play day 2 in either Crime.net or Crime.net Offline. There are five roaming guards and a small number of cameras. You can get four guards to submit; the 5th guard will have to be killed and his pager answered. Once the guards are down, you need to find the server room. Fully upgraded ECM Jammers will make this easier since the server room spawns randomly behind 1 of 3 security doors. While you're waiting on the override to open the door to the basement, look around for clipboards. They will contain clues to help you figure out which engine is the right engine. It is probably a good idea to either avoid or break the cameras (only break them if you've already taken all 5 guards out of the picture).
It is recommended to do this mission stealthily so you can avoid any further police force and concentrate more on figuring out the correct engine. If you are unsuccessful at sneaking your way through you can still succeed on the day, you will have to run back upstairs frequently to turn the lights back on and then you will be under heavy assault. Once you enter the basement, pay close attention to the points below which will help you choose the correct engine; the correct engine changes every time you play the job. Also, note that the clues are random spawns too. They may be down in the basement, they may be up in the house, and you may only find 2 instead of all 4.
One clipboard will have the name of the gas written on it.
Another indicates how many hoses will be connected to the large blue tank written on it - "# x H" in the bottom left of the clipboard. The number signifies the number of hoses that will lead to the top of the larger tank. ex. 2 x H means there will be 2 hoses, 3 x H = 3, 1 x H =1.
In the entry area at the bottom of the stairs is a big white board, it says which propellant has which bottle color. Now you can identify the bottle color of the engine you are looking for. You should be looking for the small bottles in the engine. They can either be blue, green, or orange. (You may want to bag and drop all the wrong colored ones to make it easier to run around and compare the right colored ones with the other clues)
One of the PCs has the PSI displayed in the top right corner. The display will shut off after a while!!! You need to use the PSI to calculate the bar value. Take the PSI value, divide it by 10 and multiple it by 0,7. For example: 5812PSI /10 *0,7 = 406 bar. Now look for an engine with that bar value (there is a dial attached to each engine that shows how many bar it has.)
Once you pick the engine you think is the correct one, bag it, and bring it back to the airstrip. Wait for the helicopter to pick the engine up, and throw it in once it arrives. It will take roughly three minutes until you hear back whether it was the correct engine or not; until then the alarm will go off no matter what meaning you'll have to hold out. The achievement will unlock after it has been confirmed that you picked the right engine through the radio
It's random which engine is correct, but there are some clues:
1. PC screen with PSI value in the top right corner. It will tell you whether the engine has more or less than 5812 PSI. That's equal to 400 bar. There's a watch at each engine, showing how much bar it has. 2. A clipboard on one of the tables tells you how many cables the correct engine has. It either says 1H, 2H or 3H (3H = 3 cables). These are the cables going from the big blue bottle to the engine itself. 3. Another clipboard with a green checkmark tells you whether the engine uses Nitrogen, Deterium or Helium. The white board in the entry area shows which bottle color belongs to each substance.