Most of the aid has its origin in pre-Nazi times, with the United States being one of the only nations willing to invest in the Weimar Republic. I've really only looked at the oil industry, and can only point to the research of Friedrich Bergius immediately prior to WWI into the hydrogenation of coal, which began test production in the 1920s. The western multinationals took notice of this as the technology represented a method by which a nationalist party could exclude them from markets. It became necessary for them to try to gain control of the tech, which required closer economic ties with the Germans.

In practical application, this created agreements between IG Farben and Standard Oil which marked each company's spheres of influence, for lack of a better term - one of the cartel agreements. The Germans would respect Standard's position in the energy market, while Standard would respect the Germans' position in the chemical industry. This mainly involved respecting each others' patent rights, and granting each other exclusive international licenses.

Much has been made of Standard trying to cover up some of the German rubber patents when they received them in 1939, and people have criticized the sale of rights to tetraethyl lead as aiding the Nazi war machine, but the reality lies in those pre-nazi business ties. And, in the case of Tetraethyl Lead in particular, it was a chemical additive discovered in the 1920s and monopolized by Standard Oil and GM through Ethyl Gas Corp. The Germans were well aware of what it entailed, and had the technical knowledge to just make it themselves.

The other note is that the Germans would have been well aware that the new 100-octane gasoline being proposed by Shell through the likes of Jimmy Doolittle was based in part on that original process developed by Bergius. The Americans figured out how to apply the process to various hydrocarbon byproducts of their refining operations to isolate pure isooctane, which is the basis of the octane scale. Therefore, the relationship with Germany allowed the United States to deliver blended gasoline that had the same performance characteristics as pure isooctane, the first deliveries of which arrived to the Royal Air Force shortly after the Fall of France.

The Germans really got played out on that one.