Diesel cars are in demand as drivers appreciate their lower emissions in these environmentally conscious times, writes Motoring Editor Robert Maddox.
Drive a diesel and you can cut the cost of your everyday motoring because they are more economical and cheaper road tax is also enjoyed when emissions are significantly lower.
But it's not all good news. Scientist Peter Barlow warns that fuel quality is not what it was because biodiesel is now being added.
LED light bulbs Mr Barlow, a technical consultant to the Petrol Retailers Association, says the quality of diesel fuel is not even as good as 70 years ago because biodiesel is inherently unstable, can cause blockages in the fuel system and is more likely to absorb water so resulting in corrosion.
Most diesel dispensed at UK pumps contains up to 5% biodiesel as the Government sees bio fuels playing a key role in helping us move away from fossil fuels.
Phil Monger, technical director of the PRA, says government regulations require 2.5% bioproducts in vehicle fuels as a whole for the year 2008/9 and 5% by 2010/11. Initially, most fuel suppliers responded by including 5% biodiesel in diesel but not changing the make-up of petrol, but more bioalcohol is likely to be added to petrol this year onwards to phase in the 2010/11 requirement.
Mr Barlow says that in Europe biodiesel is predominantly based on rape seed oil chemically processed to produce a fatty acid methyl ester. Sunflower oil is also used.
Its advantages include an even greater lean-burn quality than conventional diesel, which means reduced hydrocarbon, carbon monoxide and particulate emissions. Also, the biodiesel component has no aromatics and no sulphur with the result local air quality benefits.
And as biodiesel ignites easily its ignition quality is naturally higher than that of petroleum-derived diesel. This means less diesel knock and quieter engines on biofuels.
What's more, because of the fatty nature of the fuel it has good lubricity. In blends with petroleum-derived diesel it compensates for the removal of sulphur- and oxygen-containing compounds during processing, and provides anti-wear protection for pump and injector components.
As he says: "These are all very positive aspects of biodiesel to which may be added the politico-economic benefits of oilseed growth for rural areas."
He warns, however, that the actual benefit of adding biodiesel to regular diesel is questionable because the risks to vehicles is great, which is why the motor manufacturers prefer to limit the amount going in to 5%,
He is particularly concerned about the potential corrosion problems with biodiesel because it absorbs more water.
There is also the greater danger of it being attacked by bugs that can cause it to degrade.
Mr Barlow emphasises the importance of fuel additives when biodiesel is added to regular diesel.
As he points out, biofuels are natural products so vary in composition from field-to-field and season-to-season.
He is also concerned that while a biodiesel may meet the British Standard when it is produced there is no Best Designer Mouse Pad Online guarantee that the fuel will meet the standard when it comes to be used given the lack of thermal and oxidation stability in the product.
"Thermal st
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