There are 4 ways to ignite the gas trail in GTA 5! Did you know that?
Here's an interesting fact about the mission "Crystal Maze" in GTA 5:
In this mission, Trevor destroys the O'Neil brothers' meth lab to eliminate competition.
He eliminates everyone at the location, picks up a jerry can, and pours a trail of petrol outside and throughout the house before igniting the trail.
Interestingly, in the trailer, Trevor ignites the gas with a Molotov cocktail, while in an official artwork, he uses a Zippo lighter.
However, in the game, you are instructed to shoot the trail to ignite it.
Instead of doing any of these you can also burn it by performing a car burnout!
