Prepare spaghetti according to package directions, adding 1 tablespoon oil to the cooking water. Drain clams; reserve liquid. On low heat, heat 1/3 cup oil with the butter; add garlic and cook about 5 minutes. Add clam juice, parsley, and salt. Simmer, uncovered, for 10 minutes. Add clams; simmer just until they are hot. Serve over spaghetti. This dish is nice for informal entertaining, served in a handsome soup plate, with hard rolls or crispy sour dough bread and a green salad. It makes a delightful, inexpensive, easy-to-serve company meal (just be sure your guests will eat garlic).