system
Given the following post, respond as if you're commenting on Reddit:
human
[Batman] Why does fire shoot from the back of the Batmobile?

Is the Bat's vehicle literally propelled by flame like a rocket of some sort? Is that more effective than a quality engine? What kind of fuel is used to create the flames? Does it pollute more than normal cars?
gpt
The flames would be used for short bursts of speed but the downside is they would use alot of rocket fuel ir aviation fuel.

The batmobile would likely run on petrol or diesel and the rockets would be for propulsion when he needs bursts of speed. 

He would have to use them carefully because of the potential of causing collateral damage. A rocket powered car is just impractical in and around city streets. 
More likely than not he just uses the flame for cosmetic effect, intimidation, fear or awe.