WHEN we will run out of oil is subject to a LOT of unknown factors:
1) We do not know how much oil the planet has.
2) We have not even located all of the accessible reserves, for instance, we only have vague guesses as to how much oil is under the Arctic Ocean or Antarctica.
3) The amount of RECOVERABLE oil is subject to change. For example, in July of 2008 the recoverable reserve in North Dakota was increased from 30 to 300 billion barrels--equivalent to adding 45% of the known Saudi reserves.
4) The efficiency of the conversion process whereby crude is transformed into usable products is subject to improvement--which means more product from less crude.
5) The efficiency of the conversion of the end fuel products to useful energy is subject to improvement.
6) Recycling of hydrocarbon based compounds into other products is still in it's infancy. In theory, we can recycle any hydrocarbon into any other hydrocarbon. This would permit us to perfectly recycle plastics and to manufacture gasoline type hydrocarbon fuels from any hydrocarbon, including plant cellulose.
Like most such issues, the initial assumptions regarding the question are vital to how you interpret the answer.
Most analysis is conservative and assumes that there will be no new fields found, no changes in extraction or conversion efficiency and only very limited increases in utilization efficiency. Such conservative answers will over state the problem in most cases.
The overall efficiency of finding, recovering, converting and shipping oil; and finally converting the fuel to usable form is very low--the final process of conversion from gasoline to motion is only about 20%, and the efficiency of conversion of crude to gasoline is 85%, so if you start with the refinery, the overall efficiency of a gasoline engine is 17%--but that doesn't take into account drilling and recovery costs or transportation and storage costs, so the actual efficiency of the process from beginning to end is much lower.
Our problem is not oil but energy (the number one use of oil is to create heat which is either used directly or transformed to mechanical or electrical energy.)
As a space-going species, we have access to direct, unfiltered solar energy ranging from radio frequency to charged particle streams.
Since the Earth-Moon double planet system intercepts 10,000 times as much solar energy as the Earth alone, our problem is not that we lack energy, but that we have failed to collect our most plentiful source.
It has been feasible to collect this energy in orbit and transfer it to the planetary electrical grid via microwaves since the mid-1970's. The efficiency of the process is not high--only about 5% of the initial solar energy would enter the electrical grid. But since the available energy is many thousands of times that used by our civilization, and the conversion and transmission processes are subject to improvement, this is not a major issue.
The advantages of solar power satellites are many and include:
1) Space based power plants are much harder to disrupt than current systems. This makes them resistant to terrorist or other attack.
2) The energy losses in collection/conversion do not increase the amount of waste heat on Earth. (Although transmission and use on the surface do result in a net increase of heat.)
3) The systems themselves are more efficient than similar Earth-based solar collectors due to the ability to operate nearly 24 hours per day; and they do not need complicated mechanisms to track the sun.
4) Since it is cheapest and most efficient to construct such facilities in space, using material from the Moon rather than Earth, the materials and energy used are not removed from Earth and the waste products (pollution) do not have to be disposed of on Earth.
5) Because of the lack of atmosphere the initial amount of energy received per square meter in space is much higher than on the planetary surface, so the facility can be smaller to produce similar power outputs.
The main reason that this type of process is not in use today is that it requires, as do oil and nuclear power, a large infrastructure and we have lacked the economic and political will to construct that infrastructure.
If nuclear, coal and oil-fired power plants were required to completely deal with their waste products, and that cost were passed on directly to the user (instead of the current method of dumping wastes and expecting the taxpayers to foot the disposal bill,) space based power systems would be directly competitive on a total cost basis.