Fuel economy and headlights

Add in 29bhp 2cv, officially 69mph - again, abysmal drag but a low frontal area.

Probably even better than those figures. My guess would be that the VW engine (tall gearing for its day) would be revving a fair bit less that peak power revs at those speeds.

Rolling resistance of tyres increases with weight.

Julian.

Part of the fuel obviously goes to lights and heating the car. That part should only be taxed the same as domestic fuel.

Ive actually found that at 60/70/80 my IS200 manual is more economical than at a steady 50.

I've found, using the instantaneous economy clock, if I hold a very constant throttle at can get arround 50 but only 25-30mpg. If I do the same at 70, then settle the mpg meter at 40, it will hold at arround

What happens if you change down?

The GS and LS (only auto) don't get into top gear lock up till 80mph, the IS most commonly has a manual 6 speed box, so are not really comparable, usually very different engine sizes too

In the UK it isn't really feasible to get an 80mph mpg figure from our GS, but it manages 40mpg at a gentle 50 -60, I can't get it, but my wife can. The average local driving figure is 19 mpg. So the faster steadier stuff is vastly better.

All of which - except the diodes - are present in any alternator.

I think we basically know all this - well I do! But the point's been missed here, so again then, why waste fuel by needlessly and easily avoidably running with unnecessary electrical loading on the alternator? Save the pennies and the pounds look after themselves - there's a generation of people who previously lived beyond their means currently discovering this as the recession bites harder!

Julian.

What's been missed is that all modern cars with engine management systems will open the idle air valve to compensate for the lighting load at tickover and thus maintain tickover constant. That extra air also means more fuel is used. Back when cars had carbs there was a noticeable drop in rpm.

Lighting load is near constant. It's a large proportion of load when lightly loaded at tickover standing in sub 8mph city traffic and virtually negligible at high load such as M-way cruise at non legal speeds. Dim-dip wires both headlamps in series reducing lighting load to about 3/5 of normal dip beam.

As for people living beyond their means, it crosses many generations. My brother is convinced that some people in his area were not working but simply re-mortgaging to extract the increase in house value and living off that. Some house prices had gone from £1/2m to £1m in 10 years, £50k/pa isn't too bad for doing nothing.

A very inefficient way of doing things. The light/heat ratio gets very much worse with an under run lamp. Better to have proper 'running lights' using a smaller lamps.

But if you wish to increase efficiency, use HID units.

Depends - claimed as up to 10%, but that's when the compressor is running. At idle, my 1.3 Ka's engine load doubled with the compressor running. It was closer to 8% at ~55 mph. How long the compressor runs depends on the weather. When it was just over 20 degrees and after twenty minutes, my Ka's compressor was on for about half of the time. So it increased consumption by ~4% at 56 mph *however* I can vary it by far more through roundabout techniques, a bit of traffic, carrying more pies, being aggressive.. whatever. And cold winter starts were always heavier on fuel than warmer starts in the summer.

Whilst I agree with what you're saying, if the difference is so subtle in consumption, would one notice if you didn't use the headlights? One potential danger is that a given driver will not use their headlights until they deem is absolutely necessary, but in some weather and / or lighting conditions, it can make a lot of difference.

I know I would rather have my lights on and gain some safety than put them off to save a few pence per tankful. Some things are not worth economising on, especially where safety is concerned.

Indeed. All too many drivers are too stupid to think the same, though!

For what it's worth, both of my Saabs have a dark dashboard, which encourages early lighting up.

"DervMan" gurgled happily, sounding much like they were saying:

FWIW, my Saab has the dash lit all the time the ignition's on. So there. Leave the light switch on dip, and the lights all go off on the key - I don't think I've touched the light switch since about October.

Same in the 156.

Only touched the switch to flip it to main beam.

Don't need to touch the wipers other than to wash the screen, either, 'cos it has rain sensors.

Yet one more f***ing irritating and unnecessary thing to go wrong which modern cars are cursed with.

I wouldn't say that - they work really well, and if the sensor plays up, you can swap to manual control anyway.

One of those little details I miss, now I've handed it over to Mrs H.

Other stuff I miss:

Electronic handbrake Flappy paddle gearbox Decent head unit, with bluetooth and iPod controller.

And I must have one of the only MkII Ford Focuses (Focii?) in existence that doesn't have a Quick-Clear screen.

Like relays, lightbulbs, microswitches, 8-tracks...