At the Gas Station

You need to fill up the tank and communicate with the attendant.

You
Buenas tardes. Lleno, por favor, con gasolina regular.
BWEH-nahs TAR-dehs. YEH-noh, por fah-BOR, kohn gah-soh-LEE-nah rreh-goo-LAR
Good afternoon. Fill it up, please, with regular gas.
In Mexico and many Latin American countries, gas stations have attendants who pump for you. You don't need to do it yourself.
Attendant
¿Regular o premium? Y por favor, abra la tapa del tanque.
rreh-goo-LAR oh PREH-mee-oom? ee por fah-BOR, AH-brah lah TAH-pah del TAHN-keh
Regular or premium? And please, open the tank cap.
You
Regular, por favor. ¿Cuánto fue?
rreh-goo-LAR, por fah-BOR. KWAHN-toh fweh
Regular, please. How much was it?
'¿Cuánto fue?' is the standard way to ask for the total after any service. It literally means 'How much was it?'
Attendant
Fueron ochocientos cincuenta pesos. ¿Paga en efectivo o con tarjeta?
FWEH-ron oh-choh-see-EN-tohs seen-KWEN-tah PEH-sohs. PAH-gah en eh-fek-TEE-boh oh kohn tar-HEH-tah
It was eight hundred fifty pesos. Cash or card?
It's common to tip gas station attendants a few pesos, especially if they clean your windshield or check your tires.