Nothing will stick to oil stains for long, powerwashing is worthless
for oil. Rent a floor scrubber-buffer and get strong soaps, TSP ,
Degreasers etc. and clean until its clean, then etch with Muriatic acid
and check it to specs. Concrete oil stain that Sherwin wiliams carries
doesnt peel if done right . I beleive its called H.C, stain. Paint
can peel eventualy, and usualy does. Cleaning is the most important
step. It will take a day.