Don't bet everything on petrol. They have been stealing and hiding advanced energy technology at least since Tesla died (not to mention that high speed, high volume hydrogen production technologies were used during the U.S. Civil War!).
Technologies for powering, say, a single automobile car for 20 years without ever having to stop to refuel it have existed for DECADES. Part of the reason they suppress technology is that they want to appear to be a 'god-like Master Race ' helping the world when all along they've been suppressing and oppressing just so they an accomplish that kind of false unveiling. A key reason radioactive substances are hoarded (in the name of 'safety' and 'preventing terrorism') is because they are useful for generating endless electrical power, safely.
Inefficient solar cells are designed to be just that: inefficient. Someone barely past teenager developed a system back in the 90s to get solar cells up to 50%+ efficiency, he was threatened, the technology was stolen and in a half-assed form re-surfaced at a university as 'new research' 10 years later and was kept very low very to the point of disappearing into the cracks of the Interwebs.
Another case was someone had their computers hacked and home broken into after they had figured out a way to create a catalyst using aluminum plates to extract hydrogen from water: 'surprise' a few months later aluminum and copper prices (even wire) shot through the roof. Note: none of this research was being published over the Internet. The simple premise of the technology was that he noticed how aluminum bleachers and any shiny aluminum turned dull quickly in open air and that such was Aluminum's way of 'rusting' (i.e. it was binding with oxygen from the air). And behold when heated up, Aluminum (which will actually burn like wood!) will actually pull O2 from H20 even underwater.
So yes, they want to seem to be the origin and source of the technology they have stolen and suppressed and don't want it released until they are in the position to take full credit for it.