I put this question here because its more about the sporting regs, not technical regs
Article 28.something:
e) If an engine is changed in accordance with Article 34.1 the engine which was replaced may not be used during any future qualifying session or race with the exception of the last Event of the Championship.
Vettel loses ten spots for a single engine change, but unless he qualifies in the top 5 there's minimal chance of getting points. Why then would he not incur a second engine change (or 3rd) and have 1-2 near-new engines for Abu Dhabi?