petrol price prediction

[Welly]

Is it just me or does the HDi economy drop somewhat in much hotter weather?

I struggled to get 47mpg on the motorway this weekend, normally 50mpg is the norm.

[Jimmy]

Air con working harder maybe?

[rapport25]

Yes totally agree. When you have climate it tends to kick the air con on more frequently when its warmer.

I would sooner go slower and be nice and fresh when i get to my destination.

[mjb]

My guess is hotter air being pulled into the engine. The intercooler won't be working as well as in cold weather either

A/C is an interesting theory, but I don't think that's the cause because the compressor takes a comparatively tiny amount of power to drive (probably about 500W - less than half a percent of the engine's max power output?)

[DaiRees]

Hmmm, it's a curious one. Warm air is less dense than cold air, so in theory there should be less air resistance in the summer. Plus there's less electical drag, lights / wipers / heaters / heated rear window / heated seats not on so much, so I reckon you should be getting better mpg not worse. I know I'm getting better economy since the sun's been out . Unless there's something going on with the turbo diesel that I've not encountered, such as less efficient operation of the IC as MJB says.....

[TooT]

Did anyone notice i price hike today?

I filled up my van at 11am at 120.9 a liter, drove oop north and got back to the same petrol station at 3pm ish and the price was 122.9 a liter for diesel WTF up 2p in 4 hours. Its getting stupid now

[rapport25]

Yes kinda agree in theory but its proven you car uses more fuel when using the a/c so if its hot temperatures the climate will be using it more than say in the winter and more frequent. Its also true with lights on etc you use more to. Bascially everyone is right

[Welly]

I did notice last friday I was carrying out my pre-long journey 'checks' and the IC was HOT when I got home from work when normally it would be cool/warm.

The engine's management would detect diesel knock (or pre ignition) and put more fuel in I suppose? apparently 15 deg C ambient is THE optimum temperature for a turbo diesel.

[Eric]

Yeah big drops in power with turbos and hot air.
You drive harder to get the same performance so loose MPG.

I doubt air-con makes any difference at all that you'd notice tbh.

[Busman]

Over the two and a bit years that I've had the 406, I've experimented with the A/C and MPG. The short answer for my HDI 110 is that I can not get it to make any difference at all if it is turned on or off. I've tested this with the fuel computer and the old way of tank fill to tank fill. So I leave the climate control on all the time to keep the A/C nicely lubed at the interior dry.

Also, my average MPG does seem to be up a fraction in the hot weather, but only by 2-3 MPG so it is difficult to say for sure.

Interesting that someone said the compressor uses 500 watts, cause that is 2/3 of a horsepower which is not a lot.

Have fun,

Busman.

[Welly]

Certainly my MPG improves by about 3 mpg between winter and summer but I wondered if it had dropped in the recent 27 deg C temperatures.

[mjb]

Interesting that someone said the compressor uses 500 watts, cause that is 2/3 of a horsepower which is not a lot.

That was purely guesswork - an overestimate in all likelihood - based on the fact I have a portable aircon at home which uses 2.5kW at the plug and belts out a HELL of a lot more cold air than the car does...

[Jimmy]

I've noticed my MPG dropping to about 44 when it's usualy about 50 thinking about it, I'm getting some new rubber next week, i'm hopeing that will improve it a little. i have AC on all the time usualy set at 20

[Captain Jack]

ONE POUND THIRTY PENCE is the price of diesel today! What the F**K?!?!? We'll reach 1.50 mark by the summer at this rate...

[Welly]

Good grief - That's £5.90 a gallon

*reaches for the chip pan*