Been thinking about the earlier statement about it being cheaper to open a window than to run the air con. Read through posts since then, might have missed it but seen no comment to contradict it, so here's mine:
Now bearing in mind that it is just not on to mention going over the speed limit, I will restrict my example to one that safely stays within the motorway speed limit.
Example is:
Fully loaded van say a Merc sprinter, tranny Vivaro, that sort of size, with full payload, in very light traffic ( say 3:30AM ) and an uphill gradient.
You are slowly gaining on a much larger vehicle, you are going say 5 to 10 MPH faster than the vehicle in front but no way are you going to overtake like a 20 yr old Saab Ferrari eater.........you get as close as sensible and safe then indicate and pull out. yes there is a drag effect from the aerodynamics, but you are coming alongside and proceeding to get past..
Now open a window, any window but lets say in this instance the driver side window so as not to compromise the airflows more than necessary.....and watch the vehicle on the left either lock speed with you or draw ahead again.....
I doubt that turning on the aircon instead of opening the window would have such a drastic drag effect....Therefore the engine efficiency and fuel consumption would seem to be more adversely effected by opening the window than by operating the air conditioning....
Just in case anyone is thinking that there are a lot more metres cubed in a large van as opposed to a car, and acting as a parachute, this example is based on a full bulkhead type,closed of from the rear of the front seats so probably less overall cubic space than all but the smallest car
Plus it blows the froth off your pint all over the Times crossword....
