You know oil cuts oil and if the scent on these Dickie’s is petroleum based then why not fight fire with fire so to speak?
I would try washing them in the hottest water possible, but rather than using a detergent try using a real soap based product. Since its next to impossible to find real powdered soap or soap flakes anymore you could get a bar of Fels Naphtha and grate it on a cheese grater and dissolve the grated soap in some very hot water and add this to the washing machine. Wash them for the longest possible time. Then use some white vinegar in the final rinse to remove any soap scum. This could very possible work and would be an inexpensive remedy.
Eddie