Let me affirm essxjay's comments.

International flights can be upgraded with miles if you have an H fare or higher. V is a lower fare than H. However, a systemwide upgrade will work on any international fare.
BUT a systemwide will not work on E-fares because the E-fares' rules state that they are not upgradeable and the systemwide rules state that it cannot be used on tickets that state that they are not upgradeable.

However, trying at the gate can never hurt