Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_name_8 ( year INTEGER, engine VARCHAR, entrant VARCHAR )

### Question ###
What is the average year that the Belanger Motors had an Offenhauser l4 engine?

### Accurate SQL ###

SELECT AVG(year) FROM table_name_8 WHERE engine = "offenhauser l4" AND entrant = "belanger motors"