SQL & PL/SQL

Hi evebody,
I have process that use this sql request :

SELECT $code
FROM DUAL
WHERE $code IN ('BMW','MERCEDES','TOYOTA','PEUGEOT');

Actually, the code is a string which value is car brand. for example 'BMW'.

I want to change my process and have the possibility to put in $code multiples car brand separated by '||' . For example, 'BMW||RENAULT'.

In this way, howa could I change my sql request?

ie I want to check if a part of string exists in a element list's string.

PLEASE HELP ME

THANKS