A lot of four letter words come out of my mouth whenever I splash hot grease on my favorite shirt (and it happens a lot more often than I would like to admit because I never seem to learn to not wear my favorite shirt while cooking). And the one thing that regular detergent seems not to wash out is grease! Don't fret, there is a simple way to help pull that grease out of your shirt so that it isn't ruined! (This tutorial comes from the kitchn.)
Dish soap is made to get grease off of dishes. Rubbing a little bit on the grease stain will help get that grease out of your clothes. If grease gets on your clothes, quickly remove the piece of clothing. Take some liquid dish detergent and squirt some on the stained area. Gently rub the dish soap into the fabric. Let the piece of clothing sit there for a few minutes to allow the dish soap to soak into the fabric.
Then, wash the piece of clothing like you normally would. The dish detergent works during the wash with your normal detergent to pull the grease out of the fabric.