Michael McAleeranswering all your motoring queries
Why petrol pump prices are not falling
From Hugh McGahon, Dublin: Given that oil prices have now fallen to around $100 a barrel from its peak of $145 and have been no more than $115 for the past two months, the price of a litre of petrol here has only dropped around 12-15 cents in the same period. Who or what are the determining factors affecting the price of a litre of fuel at the pumps, and is there a likelihood that petrol prices will come down to a level that more accurately reflects the price of oil?
Clearly oil prices are fluctuating at present. While it was $115 when you sent your e-mail, it hit $120 yesterday morning, with some analysts suggesting a one-year forecast of $139.
There have been price fluctuations on the forecourt prices, but not to the same extent. That's partly down to the price structure of forecourt fuel. While the raw material price - crude oil - has soared and dipped radically in recent times, it's worth noting that the cost of crude represents just 34.3 per cent of the pump price. About 61 per cent goes the Government in tax and that includes a fixed excise charge of just over 44 cents per litre. Then there is the cost of refinement.
There is no doubt that some filling stations are taking advantage of the recent rise in oil prices and the consequent publicity to milk some extra profits from motorists.
However, as the closure of dozens of forecourt outlets shows, the margins in the fuel business are tight - estimated at about 2 or 3 per cent - and in many instances it's the shop and ancillary services that are the cash cows for petrol stations.
According to a spokesman for Topaz, the Irish oil distributor that is rebranding its network of 350 Shell and Statoil filling stations, the three main factors that impact on forecourt pump prices are the price of crude, the costs of refining and the movements in the dollar exchange rate.
The problem is that while crude prices have fallen somewhat, the dollar has intermittently strengthened - to a one-year high against the euro earlier this month - and that negates some of the cuts in barrel prices. According to the Topaz spokesman: "For the price of product to fall at the pump, all three variables would need to move in exactly the same way."
From Pat McCabe: I bought a new Laguna in June 2008; it now has 5,000 kilometres on it. According to the published data the car should be doing 5.1L/100km, but driving in and around Dublin I am getting only 9.9L/100km or worse. On a long trip to London I only got 6.6L/100km. Is there something wrong with the car? Also why are diesels so noisy at low speed, no problem on the motorway but noisy in town driving?
The official figure you quote is - like all these official figures - more a method of comparing one vehicle with another, rather than an achievable figure likely on a day-to-day basis.
The 5.1 L/100km figure is the combined consumption figure, which is a weighted average of two other official figures: the urban and the extra-urban figures. These are obtained in laboratory tests over distances of 2.5 and 4.3 miles respectively. In real life, several factors affect fuel consumption. These include driving style, the number of passengers, traffic conditions, and even the state of the roads.
In terms of noise, diesel engines need much greater pressure than petrol ones, and that results in a certain amount of popping and banging noises at the start. Modern diesels create a more gentle increase in pressure by injecting small amounts of fuel into the cylinder even as the piston is rising.
Diesel engines are basically going to be noisier because of the need for increased heat and pressure means that there is a bigger bang in the pistons when the engine is ignited, particularly when it's colder.
New techniques have ironed out most - but not all - of this. Some car firms have also added better sound-proofing to the engine bay to reduce the clamour.