SINGAPORE, March 25 (Reuters) - The 180-cst fuel oil cash premium slid for the second straight session to a week-low on Tuesday, on the back of robust selling interest due to lower than usual demand for the blendstock in mid-April.     The 180-cst cash premium was down 85 cents a tonne to 90 cents to Singapore spot quotes, Reuters data showed.     BP sold 60,000 tonnes of 180-cst fuel oil at premiums ranging from parity to $1 a tonne to Singapore spot quotes, at least 40 percent lower than the assessed premium of $1.75 a tonne on Monday.     Prompter cargoes loading over April 12-18 were priced at parity to 25 cents a tonne, versus $1 a tonne for parcels loading over April 18-22.     According to Reuters' analysis of shipping fixtures, only about 370,000 tonnes of western supply due to arrive in Singapore between April 11-20 will originate from the Americas, compared with 800,000 tonnes that would arrive in late April.  
  ID:nL3N0M02PW
       This could mean lower demand for the 180-cst fuel oil, which can be used as a blendstock.     Fuel oil sourced from the Americas, including the United States and the Caribbean, are typically more viscous and need to be blended to meet Asia's trading specifications, trade sources said.     In the United States, the closure of the vital Houston Ship Channel looked set to extend to a fourth day after the Coast Guard struggled to finish cleaning up after an oil barge spill on Monday. Exxon has cut production at its 560,500 barrel-per-day (bpd) refinery in Baytown, Texas.     While the channel typically affects the flow of crude oil and vessels from the Gulf Coast to refiners and terminals inland, congestion along the Gulf Coast terminals could potentially disrupt fuel oil loadings.     However, an Asia-based trader that moves fuel oil from the US into Asia said "the spill is not hampering the fuel oil business as yet."          *CASH DEALS - Four 380-cst and three 180-cst deals     BP bought from Mercuria 20,000 tonnes of 380-cst for April 9-13 at $593.50 a tonne.     Hin Leong bought from Mercuria 20,000 tonnes of April 14-18 at $593.50 a tonne.     BP bought from Glencore 20,000 tonnes of 380-cst for April 9-13 at a discount of 50 cents a tonne to Singapore spot quotes.     Vitol bought from Glencore 20,000 tonnes of 380-cst for April 20-24 at a premium of 50 cents a tonne to Singapore spot quotes.     Vitol bought from BP 20,000 tonnes of 180-cst for April 18-22 at a premium of $1 a tonne to Singapore spot quotes.     Glencore bought from BP 20,000 tonnes of 180-cst for April 12-16 at a premium of 25 cents a tonne to Singapore spot quotes.     BP sold to Mercuria 20,000 tonnes of 180-cst for April 14-18 at parity to Singapore spot quotes.          *TENDER NEWS     Vietnam's Petrolimex, which does not regularly import fuel oil on spot basis, has bought the full 110,000 tonnes of fuel oil sought through a tender for delivery over March 28 to May 9.     It will pay about $2 a tonne premium to Singapore quotes on a FOB basis for C-spec fuel oil, about $30 a tonne premium for K-spec to the same formula, and a premium of $23 a tonne to Singapore quotes on a FOB basis for A-specs.     All these specs are similar to the 180-centistoke grade fuel oil but differ in density levels. For more details, please see  
  FUEL/TENDA
       The 380-cst fuel oil cargoes were sealed at $3 a tonne premium to Singapore quotes on a FOB basis.  
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       FUEL OIL                                                                           CASH ($/T)         ASIA CLOSE      Change   % Change   Prev       RIC                                                         Close        Cargo - 180cst             602.58    -0.65      -0.11     603.23   
  FO180-SIN
    Diff - 180cst                0.90    -0.85     -48.57       1.75   
  FO180-SIN-DIF
    Cargo - 380cst             593.28    -0.81      -0.14     594.09   
  FO380-SIN
    Diff - 380cst                0.30    -0.05     -14.29       0.35   
  FO380-SIN-DIF
    Bunker                     596.50    -0.50      -0.08     597.00   
  BK380-B-SIN
    (Ex-wharf)-                                                         380cst                                                              Bunker (Ex-wharf)            3.22     0.31      10.65       2.91                   Premium                                                                                                                                                For a list of derivatives prices, including margins, please                        double click the RICs below.                                        Brent M1            
  BRENTSGMc1
                                                      180cst M1           
  FO180SGSWMc1
                                                    180cst M1/M2        
  FO180SGSDMc1
                                                    180cst M2           
  FO180SGSWMc2
                                                    Visco M1            
  FOVISSGDFMc1
                                                    Visco M2            
  FOVISSGDFMc2
                                                    380cst M1           
  FO380SGSWMc1
                                                    380cst M1/M2        
  FO380SGSDMc1
                                                    380cst M2           
  FO380SGSWMc2
                                                    Cracks 180-Dubai    
  FO180SGCKMc1
                                                    M1                                                                  Cracks 180-Dubai    
  FO180SGCKMc2
                                                    M2                                                                  East-West M1        
  FOSGEWMc1
                                                       East-West M2        
  FOSGEWMc2
                                                       Barges M1           
  HFOFARAAMc1
                                                     Barges M1/M2        
  HFOFARAASMc1
                                                    Barges M2           
  HFOFARAAMc2
                                                     Crack               
  HFOFARAACMc1
                                                    Barges-Brent M1                                                     Crack               
  HFOFARAACMc2
                                                    Barges-Brent M2                                                       (Reporting by Jane Xie)  ((jane.xie@thomsonreuters.com)(+65 6870 3495)(Reuters Messaging: jane.xie.thomsonreuters.com@reuters.net))  Keywords: MARKETS ASIA/FUELOIL