In a small sauce pan over low heat, warm the milk. Do not let it boil, it should just be above body temperature.
In a large mixing bowl, sift together flour, baking power and salt. Add oil and stir to combine. In a slow stream, add warm milk, mixing to form a loose stick dough. Turn out onto a floured surface. Knead dough for 2 to 3 minutes, until dough pulls together into a firm but soft dough. Place dough in a clean bowl and cover with a warm, barely damp kitchen towel. Let dough rest for 20 minutes.
Divide rested dough into 16 even pieces and roll into balls. Set dough balls aside and cover with a warm, barely damp kitchen towel. Let dough balls rest 10 minutes.
Take one of the dough balls, and begin to flatten the dough between your hands, keeping dough in a circular shape, about 4-inches in diameter. Place dough circle on a lightly floured surface and, using a rolling pin, roll dough out into an 8-inch circle. Place rolled tortilla to the side and recover with kitchen towel. Continue with remaining dough balls, until all the tortillas are rolled out. Once a few tortillas are rolled out, heat a dry cast iron griddle or skillet over medium high heat. Sprinkle a few drops of water onto the heating griddle. Once the water begins to sizzle and dance, it is ready for the tortilla. Place a tortilla on the griddle and cook 30 seconds to a minute or so, until the dough becomes opaque and the surface begins to toast. The tortilla may or may not puff, but a few bubbles are expected to form while cooking. The thinner the tortilla the less time it will take, so keep an eye on them. It doesn't take long for the dough to go from yummy, soft tortilla to crunch tortilla shell.
Continue will all of the dough balls until all of the tortillas are cooked. Place cooked tortillas in a tortilla warmer or wrap in a clean, dry kitchen towel until ready to serve. Makes 16, 8-inch tortillas. To store, wrap cooled tortillas in aluminum foil and place in a zip top bag. Keep in refrigerator. To reheat, take out desired number of tortillas, and make sure they are not sticking together. Reheat for a few seconds on a heated griddle. Or, wrap cold tortillas in a clean, dry kitchen towel, and microwave for 15 to 30 seconds or until heated. If heating 6 or more tortillas in the microwave, stop every 10 to 15 seconds to shuffle tortillas so that they all heat evenly.