Is sarcasm lying?
It's being ridiculous to make a [truthful] point. If sarcasm is "being untruthful," you're either too one-sided or daft to get it.
I sure hope not.
No. Lying is lying. When being sarcastic, your point or stance is obvious, if you're lying then your point or stance is not revealed at all, hence the lie.
If it is then I lie all the time.
You can have a sarcastic truth or a lie.
It's lying in an obvious way. So yes.