The answer: neither. The limo got the right fuel, but it broke down anyway, and the U.S. Secret Service doesn't know why.
"This is why we bring multiple vehicles and a mechanic on all trips," explained Secret Service spokesman Edwin Donovan in an e-mail. "Situations like this are planned for extensively by our advance teams so that the president's itinerary is unaffected by these types of issues."
The president's mechanic is conducting diagnostic tests on the protective vehicle, according to an administration official who asked not to be identified because it involved a security matter.
Despite the car-snafu, President Obama and the presidential motorcade made it back to the King David Hotel tonight without a problem, arriving there after dinner at 11:15 pm local time.
No word on whether the president speculated on the way home on whether the sort of electric vehicles his administration has embraced, such as a Tesla or Fisker, would have fared any better.