sql - Oracle Nvl and to_char function

Question

Now, I have to modify a SQL in proc, the only revision is to add a column in select clause with nvl and to_char function, no modification in the where clause.
My question is that, is this modification can cause any performance issue?

The SQL demo is like below:

original SQL:

Select a.c1, b.c2 from a, b where a.c3=b.c4

After modify:

Select a.c1, b.c2, nvl(to_char(b.c5,'FM00000000'), '.       ') As c5 from a, b where a.c3=b.c4

Thanks