HI,
The strongest degreaser I have at home is 'Challenger PC-737.'
It is not cheap, I bought a gallon from the paint store for $17.90. You can learn who may have it retail through:
Reliable Products
Elk Grove Village, IL 60007
If you use it, I'd do a spot test first. Very likely diluted will work best. It cleans surfaces I had been going over a long time with no effort.
Regards,