How Do You Choose and Use a Deep-Frying Thermometer?

The first thing to check when choosing one is its measurement range. For most purposes, frying oil is kept between 170–190°C / 340–375°F, and the thermometer must comfortably cover temperatures above this range, reading at least 200°C / 390°F. Many meat thermometers top out at 100–120°C / 212–250°F; dipped into hot oil, they will either give an inaccurate reading or be permanently damaged. Thermometers sold for candy-making and frying are made to measure both sugar syrup and oil, so one tool can do 2 jobs. Do not use a thermometer for deep-frying if its range is not printed on it.

There are two common styles. A clip-on thermometer attaches to the side of the pot, keeps its tip in the oil, and lets you monitor the temperature throughout frying; its biggest advantage is keeping your hands free. A digital probe thermometer reads faster and more precisely, but with most models the body should not be held near the oil’s steam, and the probe must be dipped into the oil again for each measurement. An infrared thermometer measures the surface from a distance; because it can give misleading results on a shiny oil surface, it is not reliable on its own for deep-frying.

The measurement location changes the result. The bottom of the pot is closest to the burner and is a few °C hotter than the oil; if the thermometer tip touches the bottom, it reads the pot’s temperature instead of the oil’s actual temperature. Place the tip in the middle of the oil, a few centimeters from the bottom and sides. If the oil is not deep enough to submerge the tip, the reading will be close to the air temperature and too low. Stir the oil 1 to 2 times before taking a reading so it better reflects the temperature throughout the pot.

Test the thermometer before using it. A thermometer dipped into boiling water should read 100°C / 212°F at sea level; at high elevations, water boils at a lower temperature, so the reading will be a little lower. In a glass of ice water, it should read 0°C / 32°F. Note any difference of a few °C and account for it when frying; analog thermometers with an adjustment screw can be corrected using this test. If you repeat the test 1 to 2 times a year, you can keep trusting the thermometer.

The thermometer proves most useful during frying. When food goes into the oil, the temperature drops; the thermometer shows how far it drops and when it recovers, and you add the next batch after it has recovered. After frying, do not place a hot glass thermometer in cold water or on a cold counter; sudden cooling can crack the glass. Remove it from the oil, lean it against the side of the pot to cool, and wipe it with hot, soapy water once it is warm. A deep-frying thermometer can also be inserted into meat, but do not dip a meat thermometer into oil.