Spilled motor oil on Front Seat: extract oil? or replace upholstry or entire seat?

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Help! Bottle of clean motor oil spilled on front passenger seat 3 days ago.1-2 ounces oil seeped through fabric into padding/cushion. I've used corn starch to absorb some, but more oil comes through fabric when you press on seat Obviously, can't sit on it without staining clothes. Can I extract all the oil? Any oil-proof seat covers? Should I cut the upholstry fabric to get at cushion? Replace cushion or entire seat?