In 2008, when the crude oil prices soared to a high of US$147 ($216) per barrel, oil companies in Singapore reacted quickly and raised the price of petrol to an average of $2.20 per litre for 95-octane petrol.
The price of oil per barrel has tumbled to below US$30 today, or by more than 80 percent, but pump price of petrol have dropped only 14 percent. The average price for Octane 95 fuel is now at an average of $1.90.

source: http://www.cozylittlehaven.net/petrolsg/
source: http://www.cozylittlehaven.net/petrolsg/

A spokesperson for one of the oil companies here, ExxonMobil, said that this was because “besides wholesale prices (of crude oil), the retail prices of products are influenced by other factors like marketing, storage, land prices, government taxes, currency exchange rates and competitive market forces”.
There are four main fuel retail companies in Singapore, ExxonMobile (Esso), Shell, SPC, Chevron (Caltex). In 2011, the Competition Commission of Singapore (CCS) had an inquiry into the retail petrol market in Singapore, to address the public’s perception that the retail petrol market in Singapore is an oligopoly among a few large, international and vertically- integrated petroleum enterprises, and so is uncompetitive or even collusive.
The CCS Inquiry concluded that their analysis showed that the structure of the retail petrol market in Singapore contains a risk of collusive or coordinated practices between competitors, but based on facts and data, there is no evidence that the petrol players are engaged in anti-competitive collusive behaviour.
The Consumers Association of Singapore (CASE) was also concerned about the retail pump price of petrol and in December 2015, had written in to the four major retailers here asking why their prices have not kept pace with the downward trend of crude oil prices.
CASE President and Member of Parliament, Mr Lim Biow Chuan, said that the oil companies responded to him, but that some of these companies refused to allow CASE to publish their answer.
Writing on his Facebook a few hours after the newspapers published that petrol pump prices have been reduced, Mr Lim urged petrol companies in Singapore to consider the interest of consumers here, make appropriate adjustments to pump prices and pass on some of their savings to consumers.
Consumers in the meantime, have voiced their unhappiness that the recent downward price adjustments were not to expectations, and that the fuel companies here have not adjusted their prices as quickly in response to falling oil prices, as they are in adjusting prices upwards when oil prices increased.