* Hundreds of cars broke down due to suspected dieselquality issues
* Incidents linked to biodiesel, Russian imports
By Ron Bousso
LONDON, March 10 (Reuters) - Britain is investigating a waveof mystery winter car breakdowns possibly linked to biodiesel orimports of diesel from Russia that clogged up filters and couldnow lead to supply disruptions and ultimately higher motor fuelprices.
Hundreds of diesel-fueled cars broke down late last yearmainly in northeast England and Scotland as a result of gel-likesubstance blocking their engine filters and leading vehiclerecovery services and the refining industry to suspect fuelquality issues related to cold weather.
The British Standard Institute launched an investigation andmembers of the UK Petroleum Industry Association (UKPIA) - BP, Essar, Esso, Shell, Phillipps 66, Total and Valero - began screeningdiesel for "filter blocking tendency" (FBT).
UKPIA said in an internal memo last week it was examiningall possibilities "including quality of biodiesel (FAME), basehydrocarbon fuel, how the product is blended and any otheradditives used."
The FBT tests will remain in place until April 15, afterwhich the results will be assessed, it said.
Ultra low sulphur diesel, or ULSD, in Britain is required tomeet the European Union standard, known as EN590, which hasanti-freezing agents added to it in winter.
While the origin and exact cause of the breakdowns remain amystery, biodiesel has been singled out as a possible culprit.
"One of the areas receiving closest scrutiny is the up to 7percent biofuel content which by EU law has to be added to allroad diesel," British car breakdown recovery service RAC said ina statement in December.
Another possible source for the incidents is Russian dieselafter tests on some cargoes of diesel originating from theRussian port of Primorsk in the Baltic Sea showed high FBTlevels, according to several industry sources.
However, pinpointing the exact source of the irregular levelis hard as fuels from different sources are blended at the portprior to being loaded onto tankers, they said. Others dismissedthe idea, saying no similar issues had been reported in otherEuropean countries which rely heavily on Russian diesel.
Britain imports nearly half of the more than 10 milliontonnes of diesel consumed last year, according to UKPIA data.
The country may face severe supply disruptions in the shortterm should the source of the problem be traced to Russiandiesel, which accounted for around 40 percent of Britain'sdemand last year, according to trade sources.
Traders fear any change to the British diesel standard couldalso lead to price increases.
"A change in the diesel specification would require allsuppliers into the European market to meet the same levels ofFBT," potentially adding to fuel costs, an industry source said.
Adding FBT tests to the British diesel standard couldpotentially increase wholesale fuel costs by up to $5 a tonne,or around half a percent, according to two industry sources.