According to the official documentation, you should be using:
config.log_level = :warn # In any environment initializer, or
Rails.logger.level = 0 # at any time
If neither of those work for you, try:
config.log_level = Logger::WARN
And if that doesn’t work, try:
config.logger.level = Logger::WARN
Note: The final method appears to be conflating the two official strategies, but works in some situations