[JohnK]

I know Amex charges 2.5% foreign currency conversion. I only use Amex for overseas purchases as I fully trust the exchange rate they will use.

I think Citibank charges 2.5% but Mastercard and Visa add on their own 1% charge. I recently withdrew money from Thailand using a CBA Mastercard, CBA Visa and Citibank ready credit at the same time and all 3 used worse exchange rates than Amex at the time. Out of those three Citibank ready credit was better than Visa which was better than Mastercard. Another inconsistency is when they process the transaction. With Citibank and Visa it was within a day or so of the withdrawal but Mastercard was a few days later.