If you have 2 cups of flour, use 1/3 cup vegetable oil and 2/3 cup milk. They'll be just fine, although as Kayb says--no butter to go on them while they're hot? Sad.

If you have NO other fat, and no whipping cream, you can use vegetable oil, but your biscuits won't be as light and fluffy. I'm also of the opinion it's pointless to make biscuits unless you have butter to spread on them while they're hot.

Oh yes, I forgot you can use whipping cream, good one but I'm unlikely to have it on hand.

whipping cream - circa 1c to 2c flour (self rising or AP w/salt & baking powder) - old recipe from White Lily flour

I'd use shortening and or margarine in a pinch. If you are using buttermilk, that will help a bit with flavor.

Do you have shortening (Crisco), or lard, or bacon fat?