This for this, I have been using gas calculator for long, in the days when ethereum fees where very low, I just ignore it and use suggested fee. Now this is where I have issues, Imtoken at most times and even trust wallet will fail or pend your transaction, it appears they collect their own charges for providing the wallet and pushes it with small fee, this I believe is Program at auto, someone can correct me if I am wrong but on one occasion, I was charged high on Imtoken but on etherscan a smaller fee was seen.