I use Spray & Wash. In the green spray bottle. It says Advanced Grease & Grass Remover. It won't get out everything, but works better than most stuff. Spray & let it soak in for about 20 minutes before you wash it.
And, I think Tide detergent does the best job on grease, too. (We used to use it to wash the floors in restaurants because it really cut grease.)