"I view oil as "stored work" in much the same way some people view money as stored work. "

I don't believe that's how Ayres' uses it. Ayres view oil as a convenient form of BTU's, which must be translated through a complex process into applied work. That "process" can vary enormously in effectiveness and efficiency. For instance, a Prius performs the same work as a similar vehicle with half the MPG, but uses half the BTU's (and half the oil). Strictly speaking, a Prius can perform the same work as a Hummer (transporting people), and use 20% of the BTU's (and 20% of the oil). An EV also does the same work as a Hummer, and uses about 1/3 of the BTU's as the Prius, and 1/15 of the Hummer's, but uses perhaps 1/100th as much oil.

"I think it makes things unnecessarily complex to reduce that far"

I'm not sure what you mean. If you mean what I think you mean, then that's simplifying things way too far.

"This might be why Hirsch chose to go that route."

I think Hirsch is simply trying to emphasize the importance of preparation for peak oil. In doing so, he's reaching for quantitative support, to give his arguments authority. He'd be far better off simply pointing to the historical record, and saying: "It's clear that oil shocks are very bad for the economy.". Everyone would agree with him, and no one would be extrapolating beyond the short-term data.

"I'd have to go back and look at the context of the 0.14 you cite because it is very suspicious to me. If it turns out that you're using it in the context Ayers intended (which paper and which page?"

Edit: I looked through the Ayres article you cite, and couldn't find the number - it must have been in another article. Instead, Ayres shows it qualitatively in the chart on page 11 (definitions are on the bottom of page 9). You can see that the correlation between E (simple energy BTU's) and GDP is not very good, as explained in the 2nd paragraph on page 12, and Ayres rejects simple BTU's as a "production function" (an equation which explains GDP growth).

"one way I could see it being valid is with the proviso that much manufacturing continue to be done by other countries"

That's not the explanation. In fact, there's an easy way to show it: world oil consumption has been flat for the last several years, but GDP growth has been quite strong, stronger than for the US (which itself has grown 8% in the last 3 years, with flat oil consumption).