The MSDS for
PRI-Gis here. It lists the main ingredient (35-45%) as
Shellsol D60. Shellsol D60 is a Stoddard type solvent, akin to mineral spirits.
FWIW, I use some Stabil in tanks for my outdoor yard equipment and stationary power equipment. I've also used Seafoam and other gasoline stabilizers. Actually, either Mex's or 2Oldman's recipes would be just as effective. More than anything, the amount of time and how much air gets to your gasoline are the two defining factors for a homeowner storing gasoline. I have some 10 yr. old gas in pressurized tanks that fires just about as good as new. I use a 6 gal can around the house and that is in a less than 3 month rotation.
The introduction of mandated Ethanol in our gas was a boon to my, then, outdoor power equipment repair business. I received some lawnmowers with price tags on the handles and a tank of 6 month old gas, a few times. The owners purchased them in the Fall, never used them, and in the Spring they would not start.