In the strictest sense, hydrocarbons, such as the alkanes, have only CH combos.
Esters have often been described as hydrocarbons with an oxygen radical structure.
Historically, ester synthesis was first accomplished with monocarboxylic (fatty) acids. The reaction of an acid with an alcohol by loss of water (in the reaction) yields an ester. The R' radical joined to the oxygen atom comes from the alcohol. Phenols, instead of alcohols, may also be used in ester synthesis. The salts of carboxylic acids may also be converted into esters using primary alkyl halides.
And then to add to the confusion, as you know, there are both inorganic and orqanic esters. Maybe we should indicate that the esters were are discussing fall only into the "organic" ester category?
The explanations I usually give are at the laymen's level, since this is not an organic chemistry web site.
If labman or any other person would like to create a white paper on organic or petroleum chemistry, PCMO/HEDO additives, or synthetic oil synthesis, I would respectfully recommend and encourage that he or she put the paper in the White Paper topical thread under the Science and Technology of Oils and Lubricant Additives section, as I make no claim to having infinitesimal knowledge (of anything). I think I can say that most websites welcome people with knowledge about specific topics that would help further understanding of complex subjects.
I simply know what I know and and am happy to share some of that unproprietary knowledge on the websites of which I am a member.
Kindest regards,
Mola