I try all the controls in a car before buying one.

Unfortunately, I've met drivers who will set the climate to minimum temperature because they think that will cool the car quicker. Perhaps it may, but in my experience climate will cool quickly and then slowly adjust itself to the desired setting, making for a more comfortable environment.

These are the same type of folk who will turn up the thermostatic radiator valves on central heating because they feel cold and then turn them down again when they feel too hot!

In hot weather, I just open the windows and sunroof for the first couple of minutes to get rid of the hot air in the interior and ducting, then shut them and rely on climate control to sort it out. In winter I have the luxury of a remote-control parking heater.

Continual adjustment of thermostats - that's womens' hormones for you!

Quite right. As a Mechanical Building Services Engineer myself (I've design ventilation, heating and A/C systems in buildings), I'm still amazed at how naive many people are as to how to use them correctly, whether in buildings or in cars.

In buildings (my Dad is one for doing this [he's not an engineer]), many people over-adjust thermostats, thinking as has been said it heats (as my Dad does at his home) or cools more quickly; in reality all that does is make people feel too cold or hot due to the sudden drop in temperature, often resulting in them 'turning the dial the other way' to compensate. Even former colleagues (mostly electrical engineers though) do this!

Its actually not sexist but scientifically true that women (especially those going through the menopause) in general do feel differences in temperature and humidity more than men, hence why they do complain more about draughts in offices etc, similarly the elderly will also be more susceptible to this.

Sometimes though it is pure ego - a few years ago, a more experienced colleague told me a (true) story of some City financial dealers who constantly complained about not having the right temperature or control of it at their desks, so the mechanical engineer came up with an ingenious plan (in cahoots with the building maintenance manager) - to have supply air ventilation grilles (the vent system fed A/C) over every desk with a 'temperature controller' serving each desk as well, but which were all dummies (the duct system was all linked and in an open-plan office, making any local changes that could be implemented worthless [as cars' dual zone climate control is]).

The placibo effect worked, and the dealers were all happy and never complained again. Problem solved, and a lesson for those with dual-zone cimate control in their cars: DO NOT set the 'zones' at different temperatures (even 0.5degC) - its a waste of time as the system will constantly fight itself (and use more fuel to do so) unless you physically divide the car into two like two rooms.

Its no different in cars - the 'thermal shock' will be exactly the same, exacerbated by the climate control ramping up the airflow rate to its maximum and moisture from the occupants' skin evaporating, making them feel even cooler, though this is a temporary effect which will disappear when the moisture has mainly gone. On A/C systems fed by refrigerants (cars and buildings) rather than via chilled water (buildings), the flow of refrigerant doesn't really vary that much, and so the air-off temperature from the grille is set at a constant, the varying factor being (like in cars) the airflow rate. This is why with such systems people feel draughts far more than with chilled water ones, where the amount and temperature of the water and thus air coming off the grille can be varied so that draughts are reduced and it feels more comfortable. Sounds great, but such systems are more prone to maintenance issues (especially leaks, not good if you have expensive items or crutial operations going on below) and as such can be more expensive to run, hence why refrigerant-based systems are much more common nowadays in buildings. Obviously with cars we have no such choice.

The good advice above should be given in the car's manual (it is in mine), to set the desired temperature, press the auto butoon and leave the car to decide how to achieve that; mine also states as above that in very hot conditions, especially when the car has been standing in direct sunlight for a long period, then opening all the windows (I tend to open all the doors and the boot even before starting up, to get as much hot air out as I can) to remove a decent amount of hot air before using the A/C.

Many tests have shown that using the windows (even fully open) is still more fuel efficient than A/C up to about 30-40mph, above that the extra drag requires more engine power to overcome it than using just the A/C. Most (including mine) climate controlled A/C systems in cars will also, in very hot conditions (e.g. car acting as a greenhouse) change the air recirculator to recirc to more rapidly and efficiently reduce the internal air temperature.

As has been said many times here, we should always use our cars' A/C systems for a good 10-15 mins once a month, even in winter, to get the oils in the system to circulate so it doesn't dry out out, causing component failures and leaks, even if that does mean having to (temporarily) overheat the car (much higher temp setting than normal), then set it back to a lower-than-usual setting (to avoid the system just using cold outside air) to reduce the inside temperature using the A/C system. A small amount of extra fuel used here will save several £000s or more in regassing and replacement parts/systems. Touch wood, mine still works fine with no new parts after 11.5 years following these simple rules.