They'll just claim the oil is enhanced with Miracle Ingredient Pu-244, for better engine performance and faster starts during cold weather. :P
(Seriously speaking, most of the oil is hundreds to thousands of feet deep; even a bunker-buster nuke isn't going to do much to the oil, one way or another.)
"D'oh"
Okay, let's just step back here for a minute, and put the normal arguments against such a thing aside.
You're Bush.
You're in the Middle East for the oil.
What the hell do you think sending a nuke 20 feet underground is going to do to the UNDERGROUND OIL RESERVES? Do you even know where oil comes from?
Re: "D'oh"
(Seriously speaking, most of the oil is hundreds to thousands of feet deep; even a bunker-buster nuke isn't going to do much to the oil, one way or another.)