If you haven't got a thermometer, a good gauge is to drop a cube of bread into the hot oil. It will take 45 -60 secs to turn golden.
It is important to have the correct oil temperature. Too hot and the churros will brown before they cook on the inside. Too cold and the churros will absorb too much oil and be greasy.
Churros can be frozen completely on the tray. Once frozen pack into sealable plastic bags. You can cook from frozen in the hot oil.
Serve churros with warm chocolate or salted caramel sauce.