Just passing along a success story about oil stain removal. After trying and failing with other products, I was able to remove some oily stains from a 1985 Hobie 14 sail using Purple Power Citrus Cleaner/Degreaser. I sprayed it heavily on one side, let it sit for about 10 minutes then used a soft scrub brush in both horizontal and vertical strokes to match the weave of the sail. I then flipped the sail over and did the same thing to the other side. I then rinsed both sides with the "jet" high pressure setting on my garden hose.
Previously I had tried soaking the sail overnight in the bath tub with warm water and laundry detergent, direct application of dish soap, and spray bottle cleaners like fantastic. Only the Purple Power Citrus cleaner did the job. I found it at Wal-Mart and also saw it at the local auto parts stores. I have no affiliation with the company.
1989 Hobie 18 Worlds boat
2007 Hobie Tiger