Bill,
I think the compound you refer to is Limonene (found in both orange and lemon oil). From what I can gather from a quick search there is about 17% more limonene in orange oil than lemon oil. So while they appear to be similar in composition, the percentage of each individual compound varies between the two species. You are correct that it makes a good degreaser, sometimes even replacing Xylene in some applications (histology for instance where it is used to dissolve human fat). I am guessing that it wouldn't be radically different than using lemon oil, given that the remainder of both products are a series of organic terpenes and aldehydes whose behavior wouldn't be radically different from limonene, but who wants to gamble with an expensive instrument over a few dollars. Just my thoughts.