Cream sugar, butter, oil, and vanilla. Add egg. Add flour, soda, cream of tartar, and salt. Mix just long enough to combine all ingredients. Roll into small balls (slightly larger than a golf ball), and then roll in sugar. Place on baking sheet, and flatten with fork. Bake at 375 for 7 - 8 minutes (they should just be starting to crack). Slightly cool on the baking sheet and then move to waxed paper.