Players could to see pricing anomalies in the months before Singapore's mass flow meters (MFM) regulations come into force.
Trade sources, quoted by the energy reporting service Platts on Monday, suggested a 'two-tier market' would develop - one based on mass flow meter readings and another on traditional methods.
They predicted that the costs of installing the meters could mean offers from suppliers vary by as much as $50 per metric tonne (pmt) for barge-delivered intermediate fuel oil (IFO).
The two-tier market, however, was likely to be short-lived. They said it would have come to an end by 2017, when all barges will have to be equipped with MFMs.
The warnings of price anomalies seem at odds with the Maritime and Port Authority (MPA) of Singapore's own assessment of its MFM rules.
It has suggested that the use of mass flow meters - averaged out over a five-year period - will push up the cost of delivering IFO by less than a fraction of 1%.
The MPA announced in April that, starting in 2017, it would be mandatory for barge and tanker operators making deliveries of IFO to use MFMs.
New tankers applying for Harbour Craft (Bunker Tanker) licence will, from the start of next year, have to have MFMs ready fitted.