You can do it if you want. The process is described in the installation guide for your OS.
For example, the following information is found in the Installation Guide for Sun SPARC Solaris:
Create a UNIX Account to Own Oracle Software
The Oracle account is the UNIX user account that owns the Oracle8i software after installation. Run Oracle Universal Installer with this user account. Use the admintool or useradd utility to create an oracle account with the following properties.
Login Name: Any name, but this document refers to it as the Oracle account.
Primary GID: The oinstall group.
Secondary GID: The dba group.
Home Directory: Choose a home directory consistent with other user home directories. The home directory of the oracle account does not have to be the same as the ORACLE_HOME directory.
Login Shell The default shell can be /usr/bin/sh, /usr/bin/csh, or /usr/bin/ksh, but the examples in this document assume the Bourne shell (/usr/bin/sh).
Caution: Use the Oracle account only for installing and maintaining Oracle software. Never use it for purposes unrelated to the Oracle8i Server. Do not use root as the Oracle account.
Sites with multiple ORACLE_HOMEs on one system may install Oracle Software with the same Oracle account, or separate ones. Each Oracle account must have oinstall as its primary group.
This was first published in October 2003