its easy to tell how amex and discover code things. Its harder for chase because they dont really provide that information. Some of my amex convience stores namely 7/11 are coded as grocery inside the store. The valeros are labeled as fuel. With discover I think they are all coded as gas stations.
CSP-$8700, Amex BCE-17.2k, Chase Freedom-$5700
Discover It-$6600, USAA MC-$5900 Ink Bold- $12k United Explorer-$5k
