English to German Tech/Engineering Petroleum Eng/Sci Bitumen

From a chemical-physical point of view, bitumens are complex mixtures of various hydrocarbons, normally classified into some main families according to their nature and rheological behaviour:

Resins, which perform a dispersing action in the asphalts in the ***oily body*** of bitumen and therefore, give it stability and elastic properties;

Wie würdet ihr *oily body* übersetzen?

Danke!