While the Balkans did net the Germans a reliablesource of oil, attempting to squeeze an invasion of the Balkans and Operation Barbarossa into the same summer was a gigantic mistake.
Moreover, building better machines is something that we have had ton of luck at over the past several hundred years and is a more reliablesource of growth than finding new easy-to-get deposits of oil and gas or decreasing the long run volatility in energy prices.