Hi, Example1 : 你最好多穿件衣服*免得*到時候很冷。 (You should put on more clothes *in case* it's too cold) *以免* basically means the same as *免得*, but *以免* is more formal, it's not used in daily conversation. *省得* is used in situations where others need you to do something. EX. 你最好多穿件衣服*省得*我還要幫你把衣服送過去/帶你去看醫生。

免得,省得 more use in oral sentence, 以免 more use in writing.

以免 mainly used in a formak occasions when we are working, we write email to our customer/vender/boss etc., we not use 免得, but if we talk them in phone, we can say 免得 省得 the tone of 省得 is more stronger than 免得. Generally it will be used when elders warned junior to do something or between the people with close relationship.