The devil is the father of lies (Jn 8:44). Yet we are not to let ourselves be outwitted by Satan (2 Cor 2:11). The devil is such a talented liar that for a challenge he'll sometimes tell lies by telling the truth. However, he times his telling of the truth to create a false impression.
For example, what the demons said to Jesus in the synagogue was true. They said Jesus wanted to destroy them and they recognized Jesus as "the Holy One of God" (Lk 4:34). At the very first temptation in the garden of Eden, Satan told Eve the truth. He said she would have her eyes opened and be able to recognize good and evil when she tasted the forbidden fruit (Gn 3:5). Her eyes were opened alright, but Satan "forgot" to tell her she would be separated from God.
Today Satan will try this trick on you. When you're watching something perverse on TV and feeling guilty, he will tell you: "Don't bother to change the channel. A commercial will come on soon." When you're not forgiving your family, the devil says: "There's no need to repent right now. It will come out alright." When you're committing sexual sin, the devil reminds you that God will forgive you. So although his statements are true, they are used to increase sin.
Jesus is the Truth (Jn 14:6), the whole Truth, and nothing but the Truth. Put your life in His hands. That's the only way you will outwit the devil.