Sorry if this has been covered many times before, but I'm not clear what rate on oanda.com I should be using for Cap1 Visa card transactions. I had thought that the great advantage of Cap1 was that there were no FX surcharges, and therefore wonder what rate I should be looking at on oanda.

The object of my research is in regard to a 30 million KRW (South Korean Won) purchase made on April 9, posted in USD on April 11. The Interbank rate tables that I see on oanda.com for April 9 - 11 are:

Conversion Table: USD to KRW (Interbank rate)

April 9:
Time period: 04/9/09 to 04/9/09.
Daily averages: 04/09/2009 1350.260
Average (1 days): 1350.26000
High: 1356.12000
Low: 1324.50000

April 10:
Time period: 04/10/09 to 04/10/09.
Daily averages: 04/10/2009 1325.030
Average (1 days): 1325.03000
High: 1352.81000
Low: 1316.83000

April 11:
Time period: 04/11/09 to 04/11/09.
Daily averages: 04/11/2009 1323.450
Average (1 days): 1323.45000
High: 1324.50000
Low: 1316.66000

and Cap1 used a rate of 1326.998154 when reserving my credit immediately following the transaction, and used a rate of 1300.099283 when posting to my statement. (The difference between the reserved USD amount and the posted USD amount was approximately $250).

To my eye the 1300 rate is 2% below the base rate at the time of the transaction, and is more than 1% below the lowest low on any of the 3 days.

I'd appreciate thoughts about how the oanda.com tables should be used.... and also whether there is any possibility that Cap1 may have started adding a 2% add-on of late. Thanks!