Diesel costs an average of 69.2p a litre in the Republic while the average for regular unleaded petrol is 73.9p a litre, according to latest figures from the Automobile Association.
The figures were compiled on Wednesday just before more oil companies confirmed price rises. However, many filling stations may not apply those increases immediately because of existing stocks or competition.
After its regular monthly review Statoil confirmed a recommended increase in regular unleaded petrol of 2.7p a litre, with diesel up by 4.8p. A company spokeswoman, Ms Martina Byrne, said, however, that the prices would not become effective for some days because of existing supplies. Commercial diesel sold in bulk would rise by 3.94p.
Texaco's marketing director, Mr Paddy Gallagher, said it would decide petrol prices on Monday. Its diesel rose by 3.8p but he said the petrol rise "won't be much".
"International prices seem to be coming down, and we are recognising that," he said.
Esso has yet to confirm its response.
Nonetheless, even with the increases, costs in the Republic are still in the lower half of a comparative table of EU diesel prices. The EU Commission's weekly oil bulletin shows diesel rose in the Republic from 60.7p a litre in January to 66.1p this month, while unleaded petrol increased from 64.2p to 73.1p.
Its figures show, however, that the UK (the only EU member-state which is self-sufficient in oil) has the highest excise costs. Statistics show that pre-tax 1,000 litres costs £260.95 in Britain and £1,040.73 after tax, compared to the Irish figures of £286.32 before tax and £661 after excise and duty have been added. Portugal has the cheapest price with pre-tax cost of £226.03 for 1,000 litres and £491.04 with all taxes.
AA figures show that since December 1998 diesel has risen 16p a litre from 53.17p to 69.2p this month. Unleaded petrol in the same period has risen by 17.54p from 56.36p to 73.9p a litre.
The AA's monthly survey of 150 filling stations, out this week, gives a comparative price study of fuel prices around the State. "It is a general index of average national prices," said Mr Conor Faughnan, the AA's public affairs manager. He pointed out that 75 per cent of service stations were independent franchises and it was difficult to track them all, but an average price from the 150 was representative overall.
The survey shows one of the lowest prices in September for diesel in Lemybrien, Co Waterford, at 64.9p a litre. Portarlington, Co Laois, and Killarney, Co Kerry, show the highest prices at 73.5p and 73.8p.
One of the lowest petrol prices (regular unleaded) is in Tobercurry, Co Sligo, where a litre costs 65.4p and Mount Merrion in Dublin at 66.7p, compared to the highest prices in Westport, Co Mayo, at 77p.
