Economic driving

Take the train if you're that concerned?

Otherwise, there's no one answer. Lowest speed in the highest gear without labouring. Match the HGV. If you drive with sensitivity to the throttle you'll be just fine. If not, simply slowing down won't make much of a difference.

Check out my article about fuel consumption on my website.

You can drive at 50mph on the motorway, but unfortunately that will make a nuisance for other motorists. However, you can get away with 60mph by following Heavy Goods Vehicles that are restricted to 60mph anyway. Make sure that the tyre pressures are correct.

Sound advice. Remember too that tracking that is way out will effect economy. Make sure that all brakes release fully, eg no sticky calliper pistons or handbrake cables. Empty the car of everything you don't need and keep windows closed.

WRT driving, using the brakes wastes fuel, so anticipation is more important than creeping a few miles an hour above your intended speed.

Chris

Open windows increase drag by about 10%, so if you need to drive with one open, have it only down a jiffy.

Low tyre pressures, binding brakes, engine in poor tune, tracking parallel in that order will lower your mpg the worst.

Modern aerodynamic cars are best at about a steady 60mph in top gear. Anything more brick shaped will be optimum slower. A van might be best at steady 50mph, or even 45mph, if it's a particularly unaerodynamic with roof rails.

Christian.

Aerodynamic resistance grows with the speed squared. So everything being equal, 50mph is more economical than 60mph is more economical than 70mph and so on. But the efficiency also depends on the rpm, hence having a good gear ratio for the speed. My Saab has an instant mpg readout. (Why is it called readout and nor writeout?). I certainly find that my Saab is very economical at 50mph and that the consumption always increases (mpg decreases) with speed, just as you would expect.

Aim for 52 mpg which is what I can get from a motorway trip at 60mph in my

Stu

Aim for 52 mpg which is what I can get from a motorway trip at 60mph in my

Stu

Yes, but there are other issues that don't vary with the square of speed. Some elements are effectively constant with speed, such as lighting, audio equipment, computer electrical consumption and air conditioning.

Fuel efficiency is actually a peaked curved, with the peak varying in speed, but usually quite shallow from 45mph-60mph, there being little to pick between. Above 70mph or below 40mph, efficiency drops off relatively rapidly.

Obviously, every car will have a different peak, depending on many factors. Just turning on the air con will raise your cars most efficient speed.

Christian.

I don't rely too much on the instant mpg readout in my car. Apart from calibration, it also depends on the slope of the road and the wind speed and direction. However, it is a useful tool for getting an idea of what affects the fuel consumption, and to diagnose a possible problem.

Cobblers. You may find that a certain car is more efficient (if efficiency is better) at 90 mph compared to 50 mph. Or it'll be more economical at 44 mph...

As you'd expect then! :)

And since you're following them, make sure you drive right up their arse for the best slipstreaming. It'll probably annoy them, but that's just a bonus.

'course, what's best for economy might not be best for safety ;o)

Cheers,

Colin.

My Focus will do over 45 to the gallon at upto 75mph, any more than about 80 and that plummets rapidly.

Contrary, the S70 only averages about 31mpg at 65-70mph, but up that to

Tim..

==================== If you're a glutton for punishment fit a vacuum gauge and try using that as an 'economy gauge'.

Steady driving without trying to maintain a fixed speed is usually best for economy - all other factors being equal!

Cic.

But don't compensate by using aircon. If your car's black, paint it white to stay cool.

As I said, it depends on the car. However, as a general rule, modern, more aerodynamic, and sporty cars generally have their most efficient speed at a comparatively high speed.

It is very unlikely, however, that any normal road going car would be more efficient at 90mph than 50mph, though, as the v squared really kicks in by then. A specialist aerodynamic record breaking car would be required for that.

Christian.

Uncannily I have access to both the same cars.

As to your S70 figures, is yours a manual or auto? I find that around 70 - perhaps up to around 75 - I can average (according to the computer) easily in the mid 30s - given a long enough run. However approaching 80, or higher, and it drops off quite sharply.

In message , Douglas Hall