In my last Forum letter, I requested that petrol firms demystify how retail pump prices move with crude oil prices (Petrol firms need to explain mystery behind pump pricing, March 13).

To date, I have yet to see a response from any of them.

Unfortunately for motorists, on top of the pricing mystery, I have also recently observed another form of price manipulation.

On March 22, I was given a 22 per cent discount off the listed price of $2.09 a litre at one of the stations.

Just over a week later, the listed price of $2.09 a litre was maintained, but the discount was reduced to 15 per cent.

This represents effectively an increase of 7 percentage points even while Brent crude during that period was trending downwards from around US$27.50 per barrel.

Various sectors like general merchandise retail and air ticketing are subject to strict laws on being transparent about displayed prices.

Retail outlets, for example, cannot display prices without the inclusion of the Goods and Services Tax.

Why then are petrol firms not subjected to such transparency rules and allowed to operate behind a cloak?

Peh Chwee Hoe