Oil stains can be very difficult! I've had success with soaking cat litter on the freshly spilled oil.
In addition to cat litter, I would use dry cement (not concrete) mix.
scrub into the oil spots with a block of wood. Let sit for 2 days, sweep off and see how it looks.
Re-apply if necessary.
Kitty litter to absorb the oil for a couple days, sweep up, and then clean with a strong degreaser and brush.
I have used a good quality dish washing detergent on old and new oil stains with great success. Squeeze the soap onto the oil stain and leave it. When it rains the oil washes away. A second squirt may be necessary. Do the squirt in dry hot weather.