What are the important points to consider when deep frying (yeast raised) doughnuts?

For deep frying choose a oil with a high 'smoke points', which means the oil does not break down at deep frying temperatures. Peanut oil, safflower oil, sunflower oil, and canola oil are good choices, although the flavour profile and stability of each oil should be considered.
Temperature and time are very important when deep frying so a deep fat frying thermometer is essential. The best temperature is 175-190°C for 45-60 seconds. If a thermometer is not available then the oil can be judged ready when a 2.5cm cube of white bread dropped into the oil browns in 60 seconds; that oil temperature will be about 185°C.