h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Today was a hot day. 30C and horrible and there I was hot and driving around in my black car wih a black dashboard and black seats and black steering wheel and black carpets. So it was hot because the air con is pants..

I know now that I made a bad choice. I thought that putting the car through the car wash was a good idea. I thought no further than all that water pouring all over the car was bound to cool it down.

OH! THE HUMIDITY!

And I by the time I realised, I couldn't get out! I drove out of the damn thing so sweaty that I might just as well have left the windows open.

Nooooooo!

What seemed like a good idea at the time to you, but turned out to be a Bad Plan?

PP.

I can think of a few shortcuts, especially ones end up crossing a deep rhyne or 10ft thistle forests or some such...

"there I was hot and driving around in my black car wih a black dashboard and black seats and black steering wheel and black carpets"

And every time you try to operate one of the weird black controls that are labelled in black on a black background a little black light lights up black to let you know you've done it?

You are Hotblack Desiato and I claim my five pounds.

You know, it hadn't occurred to me until now, but since you mention it.

And as it happens, I play in what MAY be HItchin's loudest band.

Or was that least talented?

PP.

black on black cars are not a good idea specialy if they have leather seats

My previous car was black on black with black leather seats.

You're not kidding it was a bad idea. It could not be driven in shorts in the summer. That's when I swore I would never have another black car. Then I bought another black car. (I get bored when quickly buying cars and usually look at two and have the second).

PP.

The thing I also find interesting is economy and what people regard as good and acceptable economy.

I don't think I've ever owned a car which, driven carefully, couldn't manage 50mpg.

I wouldn't want one that couldn't. Not at £1.31 per litre...

I don't think I could survive in my car at the moment without the air con..Heaven!

It dose bring the mpg down a little useing air com

Air con even

My last three or four cars have had aircon and trip computers.

My current one has cruise control as well.

I can report that, *IF* aircon does have any impact on fuel efficiency, that impact is so small as to make no measureable difference in normal driving. I've done exactly the same sixty-odd mile journey, on cruise control, with and without aircon, and recorded EXACTLY the same mileage per gallon on both trips. To me, that's sufficient evidence that air con makes no *practical* difference to mpg, regardless of whatever people may say.

That said - the other day when I rolled into a petrol station with the "Range" indicator on zero miles, I had spent the last ten or fifteen miles nursing it along the motorway at 40mph with everything (aircon and radio included) switched off. I made it!

I was musing on the air con / economy question on my way home tonight (have been to see The Spooky Men).

As a rule, air con will be used only when it is pretty warm outside. At those times the air entering the engine will be warmer. Am I right in thinking that engines run more efficiently in warm air than in cold?

If that's the case, there will a bit of balancing out going on.

PP.

Would have thought cold air would be denser therefore more O2 therefore more "bang" per cycle.

But volatile fuel would vaporise and burn more efficiently when warm. No?

PP.

Dunno, need an engineer. But engines have intercoolers to cool air intakes. Don't they cool rocket fuel to make it work better?

It's possible that air conditioning switched on might...might reduce to number of miles you get to the gallon. But it is probably by a degree that is insignificant when compared to other factors like load carried, the state of your tyres, and so on and so on. By contrast, running a fridge in your house can make an *enormous* difference to your electricity bill - I have seen the difference personally, from the times when I either didn't have one, or had one which went on the blink.

But we wouldn't be without our fridge in hot weather, would we? It seems odd to scrimp on the car a/c unit, therefore, which is a lot cheaper to run.

My ex-brother in law used to boast about his 4/30 air con in his car. 4 windows / 30 miles an hour. However, the extra drag.......

PP.

(That is not to say that he drove round wearing women's clothing).

PP.