If petrol/gas prices were locked down, how would normal consumers and the producers be affected?
If the price is higher than the market price it will lead to less people buying gasoline. If the price is lower, more people will buy gasoline. The inverse is true of sellers.

In the first case, there will be over supply of gasoline, leading to a growing inventory.

In the second case, there will be more buyers than sellers, leading to a shortage.