The green is a dye added to show that the oil is synthetic and to easily spot leaks.100% The Green sweet smelling oils are ester synthetics. Doesn’t mean exclusively ester but ester dominate probably.
Esters are formed by a chemical reaction between an alcohol and a fatty acid — this is called esterification:
Fatty Acid + Alcohol → Ester + Water
This is the EXACT same chemical process used to make:
- Fruit candy flavors and gummy bears
- Perfumes and cosmetics
- Artificial fruit flavorings
Esters have a "fatty" smell to them because they are made of fatty acids and alcohols — the only esters that have truly "fruity" smells are those used in cosmetics and pharmaceuticals, while esters used in motor oils have little smell on their own.
However — when heated, the esters definitely smell sweet — while PAO smells more like mineral oil.