Automatic vs Manual

Well why do you need to wear out your clutch when you can just leave the car in gear and still not use any petrol? What happens if you are coasting and then you jam it in the wrong gear by accident and bang, some nice valves making little dents on the underside of your bonnet.

It makes no sense to coast, in the one or two times that I have done it I felt out of control of the car. Maybe it's my driving?

Maybe.

Just make sure you select the correct gear, and you'll be fine. If this is the only reason you think it's unsafe, how is it any more dangerous when under normal acceleration going from 1st, 2nd, 3rd, then accidentally back into 2nd again?

I would like to say that I'm not advocating this technique in normal driving, just saying that it's not dangerous
 
Because it's an entirely different movement?

If you aren't doing it for fuel then why are you coasting? I just don't get it.
 
Just to see how a car behaves I guess... why do we do a lot of things? I doubt there's a person on this board who hasn't thrown a car into a corner a bit too fast than was sensible. It's technically more dangerous going round a corner at 50mph than 30mph, but sometimes it's fun to have a play.
 
Just to see how a car behaves I guess...
That's fair enough in my opinion. I do things like this all the time...

How low an RPM will my car accelerate from in top gear?
How far can I go after 0 miles remaining before the car runs out of fuel?
How fast will my car go in reverse?
 
The engine is working at far fewer revs when ticking over, i.e. when coasting, compared to engaged in say 5th gear. That alone may mean it has a longer lifespan (edit: meant to say, though this doesn't necessarily hold true due to potentially greater strain on the engine or parts from, effectively, changing gear more often).
So my reasoning is that, since the engine is working at higher revs when in gear, I am either using more fuel to turn the engine at these higher speeds or I am using my kinetic energy to turn the engine at these higher speeds. So to put it simply.. I am either moving the car forward at 50mph and maintaining the revs at 1,000rpm or I am moving the car forward at 50mph and maintaining the revs at 2,000 rpm, so the first outcome is surely more fuel-efficient.
Yes, I know rpm is not a necessarily accurate way of assessing fuel consumption, but it is sufficiently accurate for this analogy.

And I'd like to point out the difference between coasting with the car in neutral, and coasting with the car in 5th gear but the clutch (fully) down - with the car in neutral, you have to faff around with the gear stick to put it in gear; with the clutch down but in 5th gear, it is literally fractions of a second to bring the clutch up and put the car back in gear, and the transition is smooth unless travelling much faster (>65). No risk of putting it in the wrong gear at all.

Yes, it feels as though you have less control over the car - that is because the car is no longer automatically slowing you down the moment you release the accelerator, so it is as though a restriction on movement has been lifted. That is not to say you actually have less control over the car in a real-world situation.

Edit: can't say I've tried the bottom two, PMKeates. Old car so there may be random metal filings stuff at the bottom of my tank, so I try not to let it get too low, and never really considered or had anywhere to test out reverse speed.. you've got me wondering now though :p
 
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As per the AA and Department of transport.
Coasting - does it help save fuel?

Coasting - rolling downhill or approaching a junction with the car out of gear - is inadvisable because the driver doesn't have full control of the vehicle, though it used to be quite a common practice to save fuel.

  • You lose the ability to suddenly accelerate out of tricky situations.
  • You lose engine braking which takes some of the load off the brakes on down hill stretches and helps to avoid brake fade - overheated brakes require harder pedal pressures to stop the vehicle.
These days, coasting is still inadvisable and changes in vehicle fuel systems mean it won't save you fuel either.
Old car with carburettor - take your foot off the accelerator pedal with the car in gear and fuel is still drawn through into the engine. Fuel savings could be made by coasting out of gear.
Modern car with electronic engine management - fuel and ignition systems are effectively combined and controlled by one Electronic Control Unit (ECU). Take your foot off the accelerator and the ECU cuts the fuel supply to the injectors anyway so there's nothing to be gained by coasting.
Modern diesel engines - these also have the ability to shut off the fuel when you take your foot off the accelerator.
 
I purchased a focus 2l auto for a number of reasons. The Mrs doesn't know how to drive a manual (yes she could learn), in Canada the are so many bloody stop signs and traffic lights its easier and finally its a lazy way to drive and I love it.

Would I buy an auto in england? Probably not.
 
Don't know about you guys, but I was taught NOT to coast as you remove almost all control over the vehicle.

Do they not teach this anymore?
 
Coasting because the engine does less revs so it'll last longer I straight from the granddad school of irritatingly needless and unwise things to do for the sake of no gains at all. As mentioned in that quote about you suffer from brake fade so your brakes become cooked over time, doing less revs to save the engine? Well you might as well get out of the car and push it in traffic if that is such a major worry.

As for petrol consumption RPM means squat. You can be coasting down a hill at 1k revs and I could be in gear but with no throttle at 2.5k revs and we'd both be using no fuel. There's no reason to do it, it's totally pointless.

That's fair enough in my opinion. I do things like this all the time...

How low an RPM will my car accelerate from in top gear?
How far can I go after 0 miles remaining before the car runs out of fuel?
How fast will my car go in reverse?

Yes it's fair to try it, i've tried it and it's a stupid and pointless granddad technique and went back to driving properly.
 
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Don't know about you guys, but I was taught NOT to coast as you remove almost all control over the vehicle.

Do they not teach this anymore?

Yes, coasting would be an instant fail on either a standard or advanced driving test, for good reason. Sadly many people simply don't understand the implications until they are involved in an emergency situation.
 
As per the AA and Department of transport.

Cheers.

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Coasting because the engine does less revs so it'll last longer I straight from the granddad school of irritatingly needless and unwise things to do for the sake of no gains at all. As mentioned in that quote about you suffer from brake fade so your brakes become cooked over time, doing less revs to save the engine? Well you might as well get out of the car and push it in traffic if that is such a major worry.

As for petrol consumption RPM means squat. You can be coasting down a hill at 1k revs and I could be in gear but with no throttle at 2.5k revs and we'd both be using no fuel. There's no reason to do it, it's totally pointless.

The engine lasting longer idea was just a mention, I never actually thought it was significant even had any benefits outweighed the disadvantages, which obviously they don't, agreed.

And yes, RPM means squat, but were I coasting down a hill and you in gear down the same hill, you would slow down faster than me for the same amount of fuel, which makes coasting more efficient.. that's just my deduction.
 
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As for petrol consumption RPM means squat. You can be coasting down a hill at 1k revs and I could be in gear but with no throttle at 2.5k revs and we'd both be using no fuel. There's no reason to do it, it's totally pointless.


Fuel cut is usually around 1300-1500rpm so infact there would be a difference. Afterall the car has to idle with no throttle.
 
Yes, coasting would be an instant fail on either a standard or advanced driving test, for good reason. Sadly many people simply don't understand the implications until they are involved in an emergency situation.

True enough mate.

People are taught to drive correctly by the DSA, trouble is, once behind the wheel, many assume they know better because, they are driving Gods.......

:rolleyes:

What scares me is I have to share the roads with these numptys! :p
 
To be honest the only reason I don't coast because I don't like the feeling of rolling down the hill as a dead weight. It shouldn't be done, it offers no advantage and is totally unnecessary. By all means try it, experience how pointless it is, feel how warm and toasty your brakes get and then realise it's a crap habit to take up.
 
I have to agree with Dandle. Roundabouts and junctions are so much easier in an auto because all you have to do is look for a gap and put your foot down. In a manual, you are messing about with feeling for the clutch bite (or whatever it's called) which means you cannot move off anywhere near as fast and you're thinking about two things instead of one.

You aren't 'thinking about two things' atall, it's all done naturally and habitually, you don't consciously think about it.

I personally prefer manual, but auto boxes do suit the right car. Big engined luxo-barges and GTs for example. Also, my Estima is an Auto and it does suit it.
 
Auto vs Manual doesn't tell the entire story, there are shades of grey between the two sequential automatic clutches such as the ropey BMW SMG or the much better dual clutch (DCT) pioneered by Porsche and popularised by VW.

How anyone can put up with using a manual clutch in heavy traffic baffles me, get into the 21st century, the only place for your left foot is on the footrest.
 
One final thing - most of the buses are automatics round the Keele area, and there's one particular hill where they start off at the bottom doing 45 or so, and gradually slow down to about 35 before the automatic lowers the gear sufficiently that they can actually maintain their speed/accelerate.

Welcome to the world of large HEAVY vehicles!

Are you telling me that you really think with a manual 'box the bus would not slow?

I can assure you, a truck with anything upto 14 gears, empty or loaded, automatic or manual will slow on that hill (Keele Bank I guess?)

The reason i bring trucks into this is simply because most busses are based on truck running gear. :)
 
There's that, and the fact that if the buses there use the same auto as the ones round here do then it's about the worst auto in the world.

All auto's have a kickdown whereby it will drop a gear or more when the throttle is passed a certain point so there's no reason an auto would bog down if you actually press the throttle. Above that, any box within the last 20-25 years thata even a quarter way decent will have a load sensing capability and will drop a gear or at least drop out of converter lockup mode when it senses the load increase of going up a steep hill.
 
I hate automatics.
It just takes the fun out of driving, maybe because i'm young i like to rev the nuts off of anything i drive, but if i wanna go for petrol saving then i can stick it in a high gear. Also, i don't know how you'd go about wheelspinning an auto.

It makes me feel like i'm more in control of the vehicle too, where i've learned in a manual, not changing gear feels wierd as hell. Makes the driving just feel dreary.
 
I hate automatics.
It just takes the fun out of driving, maybe because i'm young i like to rev the nuts off of anything i drive, but if i wanna go for petrol saving then i can stick it in a high gear. Also, i don't know how you'd go about wheelspinning an auto.

It makes me feel like i'm more in control of the vehicle too, where i've learned in a manual, not changing gear feels wierd as hell. Makes the driving just feel dreary.

9 hours of stop start traffic on the M6 will change all that for you :(
 
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