Here's the source my wife uses:
http://ohioline.osu.edu/outside/stainrem.html
... and there we're told
"Oil stains can be removed by pretreatment with a heavy-duty liquid detergent, an aerosol petroleum-based solvent pretreatment spray, or a pump-type detergent-based pretreatment spray. If these products are unavailable, you can use a powdered detergent that is mixed with water to make a runny paste and apply that to the stain.
The heavy-duty liquid detergents or aerosol sprays are more convenient and effective. Work the full-strength heavy-duty liquid detergent into the stain or spray with the pretreatment product, then wash the garment using hot water (if safe for fabric), the recommended amount of detergent for a regular laundry load, rinse, and inspect before drying. Repeat this treatment if removal is incomplete the first time."
Hope this helps!