Will oil stains on my driveway ruin my driveway sealer?
I sealed the drive about 7 weeks ago now and it seems that the work I did cleaning the oil spots was sufficient.

My unprofessional conclusion from this experience is that if a power washer AND solvent AND 20 minutes of scrubbing doesn't get it out, it's probably a permanent part of your driveway now. 

I'm pretty sure that the asphalt beneath that stain is actually imbued with the chemicals that cause the discoloration. I cleaned off what I could and the sealant stuck just fine.