During the peak of "The Peak" in the mid-2000s several people suggested that the Saudis and in particular Ghawar was in decline. Once that happens then, it was said, the world oil output is in decline. Of course now we know different.
Its interesting that the low oil price now coincides with the Saudis getting "militaristic", e.g. Yemen and probably more action against IS and Iran - maybe there is some panic / worry there, could also explain the recent change in the succession line.
Highest price I have paid was £1.42 a litre which is ~£5.62 a US Gallon, or at today's exchange rate $8.72 a US gallon.
And you wonder why we don't buy trucks ?