What is the best way to remo ve oil stain from a shirt?

Try shampoo

Have you tried placing paper towel under stain and on top of stain and then placing warm iron on top? Sometimes the heat presses the oil into the paper towels.

Have you tried Pine-Sol or Murphy's oil soap? They have worked for me with hamburger grease stains. Also, be careful about dryer sheets as they can leave 'oil-like' stains.

I use a paste of dish detergent, baking soda and hydrogen peroxide. Let it sit on the stain overnight then scrub a bit and launder.

Also, use dish detergent rubbed into the grease stain as a pre-wash treatment.

Since you dried the garment, chances are it is now permanent. Remember for the next time, not to dry before completely removing stain. As a last ditch effort, I would try a vinegar and baking soda soak overnight, then launder as usual.

My mother taught me a trick...a bar of hand soap, but has to be Dial, gold in color. Put the dial in a dish with just a little bit of water and wait until the immersed portion turns white and goo-ie, like a creamy paste. Then work that paste from the soap into the fabric, and I mean really rub it in. Then wash as usual! Unfortunately, some dried in stains require the process to be repeated, but it has actually worked many times for me. My toughest challenge is finding that gold colored bar of Dial! Good luck.

I agree with Naomie. Since you dried it in the dryer you caold have set the stain. Try using WD40 or mineral spirits.

Theres a pink soap i use..its called a laundry bar zote i think..it works great...even if its set in..i also use it on ring ariund the collar