Not all esters have an aroma.
I have here at my fingertips a bottle of TMP esters, it is water clear and it has no smell to it. In my lab, I have a quantity of pentaerithyritol polyol ester of ISO 100 viscosity, and it does not have any aroma as well.
Some vegetable and synthetic esters (such as flavorings) do have an aroma. Unhydrogenated soybean oil stinks like road kill.
Most synthetic esters for motor oils, such as TMP, TME, PE, Di-PE, and even the di-esters have no discernable botique at room temperature.
I think what you may be detecting by smell are the additives. Some additives vary from sweet to pungent. Solvent dyes have almost paint-like aromas in concentrated form.