road speed,revs and gears

[apple tango]

But could you, if you wanted to? I mean two things: can the car go at 40 mph in 2nd gear, (many can), and can you manage the gear change?

Out of curiosity I tried it last night - I hit 40mph in 2nd at 5000 rpm.

I had a phone call from a concerned father whose son had been given a mock test by his instructor who had failed him for not remaining in a high gear when braking towards a junction where he would be turning off, even though the car started to judder ... He was also told that he should be changing from 2nd to 5th when changing up, and not drive in 3rd around town but use 5th, which, as the father said, meant that the car had no flexibility at all.

I can only think that the instructor was very eco minded, and didn't want the engine to rev above 2000rpm.

I personally think driving around town doing 30mph in 5th gear is ludicrous. Not only will you have reduced control but I would even question if it's that efficient since you would be labouring the engine. I'm of the mindset the car should be in the most efficient and appropriate gear for the prevailing speed to maintain economy, and higher isn't necessarily better in that regard.

I have to wonder if it's likely to lead to bad habits too - driving around in 5th is almost encouraging you to speed as you would feel the car will pick up and perform better as you approach 40mph and beyond.

[fungus]

But could you, if you wanted to? I mean two things: can the car go at 40 mph in 2nd gear, (many can), and can you manage the gear change?

Out of curiosity I tried it last night - I hit 40mph in 2nd at 5000 rpm.

I had a phone call from a concerned father whose son had been given a mock test by his instructor who had failed him for not remaining in a high gear when braking towards a junction where he would be turning off, even though the car started to judder ... He was also told that he should be changing from 2nd to 5th when changing up, and not drive in 3rd around town but use 5th, which, as the father said, meant that the car had no flexibility at all.

I can only think that the instructor was very eco minded, and didn't want the engine to rev above 2000rpm.

I personally think driving around town doing 30mph in 5th gear is ludicrous. Not only will you have reduced control but I would even question if it's that efficient since you would be labouring the engine. I'm of the mindset the car should be in the most efficient and appropriate gear for the prevailing speed to maintain economy, and higher isn't necessarily better in that regard.

I have to wonder if it's likely to lead to bad habits too - driving around in 5th is almost encouraging you to speed as you would feel the car will pick up and perform better as you approach 40mph and beyond.

I put my point to the lads father which was as you said that 5th around town would probably be labouring the engine, and I personally use 3rd, as do my pupils This was his point, that he thought the engine would be labouring, and that a lower gear would give more flexibility. However I have had an examiner mention that 4th could be used, but that it's a moot point.

When braking in 5th my 1.4 Fiesta will drop to 15-20 mph before juddering. It will also do 60mph in 2nd, although that's red lining it, which is something I've only done once when overtaking a tractor doing 20mph. I normally change from 2nd to 3rd at anything between 25 and 40mph, or I sometimes miss out third, and go directly to 4th at around 40mph, or accelerate to 60mph in third and then take 5th. It depends the situation.

[WS]

I personally think driving around town doing 30mph in 5th gear is ludicrous. Not only will you have reduced control but I would even question if it's that efficient since you would be labouring the engine. I'm of the mindset the car should be in the most efficient and appropriate gear for the prevailing speed to maintain economy, and higher isn't necessarily better in that regard.

In a modern diesel it is not ludicrous at all. If you are moving at a constant speed in a flat terrain, in most medium-sized cars 5th gear is not only safe for the engine but also the most economical. In some cars 4th may be more appropriate - it depends on the engine and the gear ratios of course. Most modern diesels develop maximum torque around 1500-2000 rpm; engine speeds between 1000-1500 rpm (which is the level you will get, being in 5th gear and doing 30mph) are perfectly safe for them provided you do not put too much load on the engine.

You mention "reduced control". Reduced control of what exactly? Either you have a reason to be in a gear providing you with high performance, or you do not have it. If you do not, there is little sense in being in a low gear as this only leads to wasting fuel.

[fungus]

I personally think driving around town doing 30mph in 5th gear is ludicrous. Not only will you have reduced control but I would even question if it's that efficient since you would be labouring the engine. I'm of the mindset the car should be in the most efficient and appropriate gear for the prevailing speed to maintain economy, and higher isn't necessarily better in that regard.

In a modern diesel it is not ludicrous at all. If you are moving at a constant speed in a flat terrain, in most medium-sized cars 5th gear is not only safe for the engine but also the most economical. In some cars 4th may be more appropriate - it depends on the engine and the gear ratios of course. Most modern diesels develop maximum torque around 1500-2000 rpm; engine speeds between 1000-1500 rpm (which is the level you will get, being in 5th gear and doing 30mph) are perfectly safe for them provided you do not put too much load on the engine.

You mention "reduced control". Reduced control of what exactly? Either you have a reason to be in a gear providing you with high performance, or you do not have it. If you do not, there is little sense in being in a low gear as this only leads to wasting fuel.

My last car, a Seat Ibiza 1.9 TDI was decidedly uncomfortable around town in 5th. In fact 4th was not ideal. It was always better in 3rd in a 30mph limit.

[Gareth]

My last car, a Seat Ibiza 1.9 TDI was decidedly uncomfortable around town in 5th. In fact 4th was not ideal. It was always better in 3rd in a 30mph limit.

Similarly, when driving our Skoda with a 1.9 TDi engine, in 30 mph limits I find I frequently use 2nd and only changing up to 3rd when I can easily maintain 30 mph.

[TripleS]

I think I'm in agreement with most of what WS says.

Obviously one needs to take account of what different models of car are happy with, but that requires us to have the ability to judge what the cars are happy with, and not all drivers are particularly sensitive to these things - some do tend to bash on regardless.

Some cars are fairly happy at low speeds in high gears, but they're not all like that. It also depends on how skilled or unskilled we may be at handling them in a way that maintains comfort conditions for them. In the case of our 406 HDi I find it can be driven without any sign of distress down to about 30 mph in 5th gear, which is just over 1000 rpm, and this is quite usable in certain types of town driving - and there again "town driving" is not all the same.

As for the matter of being in a responsive gear, I have been with people who drop down into 2nd gear as standard procedure whenever they enter a 30 mph limit, but I don't do that. I've never understood this business of wanting to be in a responsive gear all the time, and I don't remember ever finding that I've been disadvantaged or inconvenienced in any way by being in too high a gear. I have invariably found that when the circumstances suggest there is likely to be a need for a lower or more responsive gear, I've been able to recognise that potential need early enough, and take the gear before the need actually arises, if in fact it does.

The main thing I'm still in doubt about is the effect on fuel economy of being in high rather than low gears, but I'm slowly coming round to the view that (despite what I had long felt to be the case) high gears are not necessarily best for optimum fuel economy.

Best wishes all,
Dave.

[IVORTHE DRIVER]

As someone who is happy to tootal through towns at 25/30mph in 4th gear I tend to agree with above gentleman, just how often in a town/built up area do you need the acceleration/response a lower gear will give you?

If my car is happy at 30mph in 4th I will only drop down a gear on leaving the 30 limit if I need to overtake the car in front and even then I will have followed said car some distance anyway to see if they are not going to increase their speed so a drop down may even then not be needed as the chances are some speed will already (hopefully) have been gained, from around 40mph my car pulls like a train so 4th will take me very quickly past the car and well over the limit given the chance.
If on leaving the limit the other vehicles move up to the N/S then 4th gives you all the response you need to follow without inconveniencing others behind.

On a similar note to above is it just me who really hates those drivers that overtake as soon as they leave a roundabout without first waiting to see if the lead car is also going to accelerate? .... the number of near misses that occur when the overtaking driver is out-accelerated by the other car makes you wonder where their brains are

[tonyh1950]

I have been reading all your posts re comfortable cruising gears with a diesel and have of course been playing with different gear/rev combinations etc. The engine is a 2.0tdi 6gear manual. My main concern is that when driving on test I do not appear to be always in either to low a gear or tohigh a gear when in an urban enviroment.
Obviously 2nd/3rd are the working gears and it appears that third has the most flexability.,2nd seems to rev high when above 20mph (2500rpm) 3rd revs at 1500rpm when doing 20mph but has enough torque to be flexable and happily goes at 30mph without excessive engine strain.
I'm happy to drive in third and the car appears to me me to be flexable enough to negotiate most hazards without strain. Forward vision and anticipation means greater control with accelerator sense and I certainly do not want to travel down a road in 2nd all the time as that seems to be a very basic form of car control.
I suppose what I want is a ROSPA examiner on this forum(ha ha) to give me a definitive answer as to to whether I would be penalised if I drove in third when I thought it appropriate.
I suppose I am too aware of engine noise. My old Saab actually was most comfortable in 2nd (petrol 2.3 225bhp aero) and it was not revving excessively at 30mph. The diesel seems to me to be screaming although I guess it isn't.
Thanks for your comments so far and I look forward to the definitive answer but I guess there is't one.

[Renny]

,Snip>
I suppose what I want is a ROSPA examiner on this forum(ha ha) to give me a definitive answer as to to whether I would be penalised if I drove in third when I thought it appropriate.
<snip>
Thanks for your comments so far and I look forward to the definitive answer but I guess there is't one.

I think you have worked out that there is no definitive answer. It all depends...
Different cars have different characteristics for torque delivery, in addition the gradient of the road may vary, as may the load on/in the vehicle, even the wind speed and direction. These also can affect which gear is suitable at that particular time.

There is no hard and fast rule. If you have any thoughts that you need to explain your actions, that can/should be included in your commentary.

[kfae8959]

I suppose what I want is a ROSPA examiner on this forum (ha ha) to give me a definitive answer as to to whether I would be penalised if I drove in third when I thought it appropriate.

I'm not a RoSPA examiner, although there are some around these parts. I did drive for one some years back in a car with a torquey, six-cylinder engine that would pull from 1500 and rev happily beyond 6000. One of his comments at the end of the drive was, "well, we can do an awful lot in third these days, can't we?" I think he was observing very gently that there are other cogs in the box!

One comment I've found very helpful was to the effect that there's no such thing as the right gear, only the wrong one. I wonder if you're letting road speed influence your choice of gear too much? Is a good gear one that works for what you're doing now, or one that works for what you plan to do next?

David