Copying this from whatcar about the supposed magical 55mph been the most effiecient speed for most cars. Fuel economy: making every gallon count - The test findings - What Car?

Test Findings

"Using high-tech fuel-flow meters and the latest satellite-navigation timing gear, we measured economy at a steady 30mph, 40mph, 50mph, 60mph… all the way up to 100mph.

To make sure our results weren't applicable to just one make and model, we tested five cars from five different manufacturers - a Toyota Aygo, Nissan Qashqai, Volkswagen Passat, Citroën C4 Picasso and a Land Rover Freelander.

So is 55mph really the efficient speed that it's often made out to be? In short, no. Peter de Nayer said: 'The results of our tests disprove the idea that there is an optimum cruising speed - around 55mph - below which fuel consumption increases.'

What the results did show was that, basically, the slower you're going in top gear, the more miles per gallon you're doing.

Don't think you can go only a little bit faster and use only a little more fuel, either - the amount of fuel burned every mile rises exponentially the faster you go.

It's all down to wind resistance - the greater the wind drag, the more work the engine has to do, so barrel along at 100mph rather than 50mph and your engine will use roughly five times the fuel.

You'll cover twice the distance in the same time, of course, but that still works out to more than double the fuel for every mile travelled. This doesn't mean you should drive around at 10mph in sixth gear. For one thing, it wouldn't do your car much good, and you may as well walk (quickly).

Still, you might be surprised how much you could save by knocking just a few mph off your speed and changing up gears earlier. How much you can save depends what kind of driving you're doing.

M-Way Driving

It's a bit of a pain that economy nosedives as we go faster, since motorways are intended to get us to our destinations quickly.

A steady cruise is also the most efficient way to drive. However, pootling along at 30mph would be a drag and probably not very safe.

You might find yourself in trouble with the law, too. In January, a 58-year-old woman was banned from driving for a week after being caught driving at just 10mph along the M32.

Still, the motorway is where the biggest savings are to be made. Realistically, in good weather and traffic conditions, drivers do over 60mph. It's how much faster you go that matters to your pocket.

Take a small family car like the Nissan Qashqai. At 60mph you'll be doing 39mpg, yet at 90mph you'll be doing about half that.

Yes, you'll get where you're going a bit quicker, but you'll be throwing away an extra 11p every mile. That's £10 on a 90-mile journey. Do that a couple of times a week and it could set you back an extra £1000 a year.

It's not only money you'd save. The UK Energy Research Centre estimates that proper enforcement of the 70mph limit would slash CO2 emissions by 3.7 million tonnes.

Lowering the limit to 60mph would cut CO2 by a further 3.5 million tonnes. That's the equivalent of taking three million Ford Focuses off the road.

Slower Roads

It's not always so easy to cruise at a steady speed on slower roads, but you can still save a packet. Just because you see a white sign with a diagonal black slash through it doesn't mean you have to hit 60mph.

Stay at 40mph, slot your car into as high a gear as possible and you'll save around a quarter in fuel bills.

That's before you consider the extra braking and accelerating you'd have to do for tight corners from higher speeds.

Higher Gear, Higher MPG

Use top gear whenever possible. Potential fuel savings are huge: use sixth gear at 40mph and you'll save about 20% compared with fourth.

You might be surprised how early you should change up for efficiency. In a family car like the VW Passat 1.8 TSI, you should be in sixth by 40mph.

Some BMWs and cars like the Audi A3 1.9 TDIe have built-in gearshift indicators to help you maximise fuel efficiency.

If you spend a lot of time cruising on the motorway, look for a car with a 'high' top gear (its engine will be turning more slowly than a car with a lower top gear at the same speed).

The Land Rover Freelander 2.2 TD4 auto is a great example. The official average consumption figures suggest it uses 25% more fuel than the smaller Nissan Qashqai 1.6.

However, our test shows the Freelander actually uses less fuel above 60mph, and it's all down to the Freelander's long sixth gear, compared with the Qashqai's shorter fifth.

The slow speeds and stop-start nature of town driving make saving fuel trickier. Here it's all about pulling away slowly and smoothly, changing up early and anticipating road conditions ahead to maintain momentum.

Saving Money Quickly

Many motorists will happily scout around for the cheapest fuel prices in their area.

Pay 2p less per litre when filling up an average car and you'll save £1.20. Not bad, but drop your speed from 90mph to 70mph on the motorway and you will save that in around eight minutes. Much better.

That's not all. Lowering your speed and using a higher gear will put less strain on your car's engine, so the chances are that it will last longer.

You'll also enjoy a much more relaxing drive, boost your chances of staying safe and cut carbon dioxide emissions as well."

This is my findings with my car too. 45 to 50mph in 6th is about the optimum for economy if you just want to pootle along. I have noticed a startling difference between 70 and 90 on the m-ways too.

Sometimes I just say sod it, and use a bit of beans. Life's too short.

If you buy a VRS, economy goes out of the window

i can get 40-45 mpg if i follow the SAFED way going to and from work, 35-40 on a normal drive and about 33 mpg if i boot it to work. from book figures there is only a 2mpg between a 2.0fsi and a vrs. so its probably achieveable in a vrs.

The optimum speed will depend completely on the vehicle.

It's common sense that lower speeds are more economical, as the the drag force holding the car back increases in proportion to the square of the velocity. Double the speed and there is four times the drag force. The key to economical driving is to keep a constant speed and be in the highest gear that is comfortable for that speed.

The 55mph thing is just a compromise beween making progress, not causing a hazard to other road users and getting reasonable fuel economy.

55 seems to be a good place to start looking for your optimum but isn't by a long way.

I can't say i like the stay at 40 in the NSL suggestion though. That can cause a lot of tailbacks and rash overtaking. 50 maybe, but 40 in a 60 is just annoying; especially when they are a member of the 40 everywhere club.

I think I get better than 20 mpg at 90 mph in the vRS (on a private road and de-restricted Autobahn of course )

i did write to skoda last year to ask for the sweet point in the engine for optimuim speed and fuel efficiency and just got quoted l/100km for urban etc. no speeds or rev range or anything like that.

Find your peak torque figure and if you can sit at around that mark in top you're going to do well on the fuel.

Yep, thats not a bad rule of thumb - sit somewhere around your peak torque figure as that should be when your engine is most efficient.

I hate these sort of articles, people who believe that trundling round at 1000rpm in 6th at 30mph is good for their car or is safe driving needs their license removing from them imho.

here's my graph from the rolling road event just after i got the car http://www.jkm.org.uk/performance/Misc/Gallery/rollingroaddays/BRISKODA%2021%2007%2007/Briskoda%20Plots%2021%20July%202007/RE07.gif

so you saying the optimuim point would be 3.3k rpm? i thought after 3k rpm that the fsi cuts in and starts squirting more fuel in?:confused:

ive found revs at 1.5-2.5k rpm was better from experience with the car.

On a tight road, the biggest thing to make your fuel economy better is to learn to drive properly. If you read the road then you can anticipate things better then you can judge your speed better. Carry more speed through corners by using the road properly and not stamp on the brakes 5yds away from the start of the corner. The last thing we need is somebody advocating driving at 40mph on the majority of country roads where there are enough selfish idiots already driving like that.

Theres no such thing really as an optimum speed due to variable speed limits.

What the article is saying is that the slower you go the better the mpg (Fact).

Obviously going too slow for the road is stupid. The point of me posting this was basically to say that this 'Optimum Speed' thats banded around in pubs doesn't exist.

55mph on a m-way is probably the most optimum you can get as mpg will be high and its realistically the lowest speed you could get away with.

Just basic physics really!

One of the best ways to save fuel is not to have SWMBO in the passenger seat.

That way you won't want to speed up so that you reach your destination before the point arrives where you feel that life imprisonment is a better option than to listen to any more criticisms of your driving

The 55mph myth came about from the 90kph (56mph) test in the original European comparitive economy test regime giving the best results (others were urban, with use of 4th and higher gears banned, and 75 mph).

The 55mph myth came about from the 90kph (56mph) test in the original European comparitive economy test regime giving the best results (others were urban, with use of 4th and higher gears banned, and 75 mph).

.......And that must go back to carburettor and distributor cars...........

Phil

.......And that must go back to carburettor and distributor cars...........

Phil

It does.

It will be dependent on many factors; power/torque/weight/wind direction/incline/tyre pressure, the list is endless

I get 38-40 in my mk1 vrs between brawdy n bristol.

thats on adv, when usin the cruise set to less that 55 i uses more fuel on adv than if i set it to 65ish were i get 36-38mpg.

when drivin myself i speed up on the downs and take it easy up. never dropping below 50 coz i dont want to cause an accident. i can get 38+ mpg this way. it also depends on hoe you aproch junctions too, i try to let the car slow naturally and get quite a few free miles that way.

well one of many ways is to try http://briskoda.net/racing-advanced-driving-techniques/safed-economy-driving/117623/ for tips on fuel economy or even try something like the Institute of Advance drivers or Rospa as planning ahead can save fuel too. I tried the SAFED thing out properly this morning on the 10 mile drive to sinisters house and nearly hit 50mpg in a petrol, could only manage 44 from there to work 5 miles away.

another tip is to have instant mpg showing and aim to keep it above 45mpg if going along a straight flat road its not looking ecomical then let off the gas slightly and press again slightly, you wont notice any difference is speed but fuel consumption then improves and will see a higher mpg on the display. I can get better mpg doing this than i can with cruise control on as i can plan a head and get off the gas in advance as well as plan for downhills and nice country roads where you can roll some sections and cruise would restrict you and then fire some fuel in to maintain the given speed it was set at.

Even without the "instant mpg" display, you can save an amazing amount of fuel by accelerating up to cruise, lifting until the car starts to slow down, then applying just a fraction more power again.

Even without the "instant mpg" display, you can save an amazing amount of fuel by accelerating up to cruise, lifting until the car starts to slow down, then applying just a fraction more power again.

want to be my translator mate, you couldnt have put it in a shorter and more understandable sentence if you tried

want to be my translator mate, you couldnt have put it in a shorter and more understandable sentence if you tried

How about:

Just blip your throttle (when necessary) to maintain your speed! Tha way your only using the engine for half the distance.

If you have a Diesel with a DPF & the DPF is too cool to regenerate the car puts in more fuel to warm up. So if you drive faster you keep the exhaust hotter, not quite sure what the optimum speed is.

Interestingly our Superbs economy is a lot better in the Summer in the south of France than it ever is in the cold damp UK, & thats with the air con presumably working harder :confused::confused: