WD-40 is a wonderful product indeed.... if that still doesn't work, take a piece of pipe and stick in on the end of your ratchet, now use the extra extension as more leverage.... if that dosen't work, have someone stand next to the car, wrap your hands around their ankles, then push on the wrench/ratchet with your foot, the person stading there will keep you from sliding and it should work....
BTW: do not try to pry very hard on tools unless they are guaranteed (craftsman, snap-on, husky, etc)