I just made 2 identical charges in some foreign currency, a few seconds apart. I used a Chase card for the first charge and a Cap one quicksilver for the second.

The dollar amount with the Chase card was about 0.5% higher than the Capone!

I thought that these credit card companies are using mid market wholesale rates or something like that, and never imagined such a huge difference could be possible.

Anybody has some insight on how this works? Is it perhaps that one bank has a longer lag in updating their conversion rates and therefore would sometimes be higher and sometimes lower than banks with a shorter lag? If not, which credit card companies generally use the conversion rates which are best for the consumers?