ORIGINAL: downunder
An engine that's tuned correctly and used for it's intended purpose (car, plane, heli, boat) will reach whatever temp it gets to. The thing with car engine temps is that most who use cars have never had any other experience with tuning an engine so can't tell by ear when it's tuned correctly. A plane engine is dead easy to tune by ear because there's always a high and almost constant load with ground running but this can't be done with a car so it's trial and error. When you know what to listen for with a car then you'll never need a temp gun.
I find it more easy to tune a car engine than an airplane engine (perhaps because I started with cars)... and tune them without a temp gun.
Sadly, nearly every new car drivers rely on the
DAMN temp gun (and often sets the engines too lean), and don't learn to listen to the engine.
In the nearby car club, the top driver’s mechanic (father) spends A LOT of his time to adjust the engine, because he only adjusts the engine by the bloody temp.
He don’t realize that the temp of the engine is changing because of the surrounding temp, humidity, the amount of fuel in the tank, way of driving etc. etc.. And he doesn’t understand that the idle mixture is mainly controlled by the high needle screw: Ones the high needle and the low needle screws are properly set, the only thing to adjust is the high speed needle.