"Well... Now that is an odd question, I mean I imagine that there are many things in this world that you do not know, but then again who does, know everything that there is to know, I mean. I certainly do not. I wouldn't be too hard on yourself about it though, it's a shortcoming that we all share."

Okay maybe humor isn't the best tactic to take with Optimus Prime, but it's at least fairly obvious that he's not lying out of ill intent for once in his life. He just wants to spare his own chassis.