Wash spinach; drain. Cover and cook in 2-quart saucepan over medium heat with just the water that clings to the leaves 3 to 10 minutes. Rinse spinach in cold water; drain. Press spinach against side of strainer with back of spoon to remove excess
Place spinach, eggs, oil and salt in food processor or blender. Cover and process until smooth.
Make a well in center of flour in medium bowl. Mix in spinach mixture thoroughly. (If dough is too dry, mix in a few drops water; if dough is too sticky, mix in a small amount of flour.)
Gather dough into a ball. Knead on floured surface about 5 minutes or until smooth and elastic. Let stand 10 minutes.
Divide dough into 4 equal parts. Roll one part at a time into paper-thin rectangle on generously floured surface (keep remaining dough covered). Loosely fold rectangle lengthwise into thirds. Cut crosswise into 1/4-inch strips. Unfold strips and place in single layer on towels; let stand at least 30 minutes until dry. (If using pasta machine, pass dough through machine until 1/16 inch thick.)
Heat 4 1/2 quarts water (salted if desired) to boiling in large pan. Add fettuccine. Cook 3 to 5 minutes or until firm but tender (al dente); drain. Begin testing for doneness when fettuccine rise to surface of water.