Hi Michael - I have no idea if this solution will work on an older stain, however the way our that the Tide Stain Brain says to get it out can be found here:

http://www.tide.com/en-US/stains/solu...

I have also pasted the steps below:

WASHING INSTRUCTIONS
1) Brush the excess stain off the surface of the fabric.
2) Rinse in water to dilute the stain.
3) If your garment is ALL WHITE, use a PLASTIC bucket to create a soak solution by adding 1/2 use
chlorine bleach per gallon of water. Allow the garment to soak for up to 30
minutes, weighting the item with a WHITE towel to keep it totally
submerged. Note: Treating colored garments with chlorine bleach can fade and significanly change the color.
4) Wash in warm water with 1 use of Tide®.
5) If stain remains, repeat steps before drying.

Good luck!