Research Base - Scorched Earth
Destroy 4 fuel tanks.
You'll spot the first tank right after you begin following the tracks, at the top of the first hill.
As you near the main gate of the base, you'll spot a pair of snow vehicles. You can explode the tank on the rear vehicle.
Found immediately after the frozen lake. There's a trio of vehicles, and you can blow up the rear one again.
This one's a little tricky. When you head down the gondolas lines to where Jonah is being held, stop at the last tower. Look to the courtyard below to spot the last fuel tank.