LONDON, Aug 23 (Reuters) - Gasoline refining margins innorthwest Europe fell sharply on Tuesday as crude pricesadvanced, but stronger export demand to the U.S. and West Africaand refinery outages provided a floor.
* Declining inventories on both sides of the Atlantic openedthe arbitrage out of Europe to the U.S. East Coast, with severalwinter-grade gasoline cargoes booked in recent days.
* Around 1.5 million tonnes of gasoline and naphtha havebeen booked on the transatlantic route to load in August,according to Reuters shipping data.
* Interest in shipping gasoline from the Mediterraneanregion to the Middle East has also picked up this month.
* Arbitrage economics for sending reformate from ARA toChina are improving, traders said.
* Petroineos chartered the MR Aquarius to load a 40,000tonne cargo at the UK port of Finnart on Sept. 1 to go to China,according to shipping reports.
* Refinery outages in Europe are also tightening the marketand boosting margins.
* Total has shut down the fluid catalytic cracker at its102,000 bpd Grandpuits refinery for maintenance lasting severaldays, a spokesman said.
* Romania's 100,000 bpd Constanta oil refinery is running atreduced capacity after a fire on the vacuum distillation unit onMonday.
* Graphic: Global refined oil stocks (http://tmsnrt.rs/2br1O3U)
GASOLINE
* There were no Eurobob trades during the afternoon tradingwindow. There were no bids or offers.
* Some 8,000 tonnes traded in the morning at $474-$475 atonne fob Amsterdam-Rotterdam, compared with $485-$486 a tonnefob on Monday. Gunvor and Total sold to Shell and BP.
* There were no trades of premium unleaded gasoline barges.Bid and offer discussions emerged at $495-$497 a tonne fob ARA,little changed from trade the previous day.
* The September swap stood at around $489.50 a tonne at theclose, up from $486 a tonne.
* Gasoline barge refining margins fell to $7.73 a barrel,from $9.50 a barrel on Monday.
* Brent crude oil futures were up 72 cents at $49.88a barrel by 1543 GMT.
* U.S. August RBOB gasoline futures were up 0.62 percent at 1.4934 a gallon.
* The U.S. gasoline crack
NAPHTHA
* Trafigura sold to Koch a cif NWE cargo at $397 a tonne, upfrom trade on Monday at $389-$390 a tonne
* The naphtha crack was at around minus $4.68 a barrel,little changed. (Reporting by Ahmad Ghaddar)
BP (BP.)