Use of Index in where clause under delete statement

Does where condition in delete statement looks for an index

 

for example:

 

delete from mytable where insertedon>='2015/02/01'

 

if there is no index on mytable does it go for table scan (among millions of records) 

 

as per my understanding (please correct me if i am wrong) , if there is no index on a table then DML operation will work fast as there is no index maintenance.

 

Thanks,

Manish