[coelodonta (OP)]

I am trying to find what the typical composition of heating oil be, does it have any marker compounds - VOCs/PAHs that would help to differentiate it from a non chlorinanted hydraulic oil

The reason i am interested in this is that I am trying to assess the extent of 2 contamination plumes within the ground/ groundwater. The plumes may be in part superimposed.

one of the plumes is from a hydraulic oil source and i have been able to test a sample of this oil, but can't get a sample of the heating oil for testing.

If I can understand what the composition of the heating oil may be, i stand a better chance of assessing what areas have hydraulic oil contamination, and what areas have heating oil contamination.

[Bored chemist]

Not an easy question I'm afraid.
Heating oils are usually straight fractions from crude oil , exactly what boiling range etc depends on the intended use and also on what's available cheap at the refinery.
Hydraulic oils can be petroleum fractions too but some of them are polyethers, glycols and other things. If you are lucky then the 2 plumes you are looking at will be different enough to be able to tell them apart.
What's in the hydraulic oil sample?