Gears - Labouring Debate

Arthur Hucksake

Arthur Hucksake

Arthur Hucksake

Soldato
Joined
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Nottingham
Hi OCuk,

Wonder if you can help solve a debate. Simple question.

What is generally more fuel saving effective.

1) Driving everywhere urban (30mph) zones in 3rd gear.
2) Using 4th with slight labouring in built up parts to none on clearer stretches.

Talking VAG diesel engines here. Golf TDI, Fabia 1.6 etc

Cheers
 
Why not just shift down to 3rd when it labours and go back up to 4th when you get into the high 20s/30+?
 
Completely depends on the car really, some can do it in 5th fine, others will need 3rd. Perhaps use 4th on the flat and change down to 3rd when you get to an incline?
 
MORE SPEED said:
Completely depends on the car really, some can do it in 5th fine, others will need 3rd. Perhaps use 4th on the flat and change down to 3rd when you get to an incline?
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Exactly. It's a bit of effort, but just select the right gear.

A labouring engine doesn't feel nice and high rpm obviously wastes petrol.
 
I personally use third in my car at 30 or so. In fact when I'm in a rolling stop start queue on the motorway and find myself in 4th at 30mph I can see the MPG-o-Meter climb (get better) as the revs increase, applying a consistant amount of pressure on the throttle, up to around say 1,750RPM (3L NA petrol not a turbo bag diesel).

I find that, for instance, 4th gear at 50mph uses the same MPG as 5th gear at 50. MPG is linked mostly to how much work you're asking the engine to do (I.e. how much you're pressing thr pedal) rather than RPM, within sensible RPM ranges of course.

Being in 3rd has other benefits as well like acceleration, engine probably likes it more, you can slow down and then speed up without having to change down...
 
Arthur Hucksake said:
Scarily, this is a driving instructor were talking about.
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Totally OT on driving instructors, but why is it that almost every single learner driver is sitting ridiculously close to the wheel. Certainly all female learners anyway. They will get some serious airbag injuries in case of an accident!

Unless everyone is 5'1", of course :p
 
Arthur Hucksake said:
That's what I do. My car sounds like its struggling in 4th below 35mph though, but the mpg meter says otherwise.
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Well it depends entire on the gear ratios and the particular engine.

That's why it has to be the driver's judgement.

Although cars these days to include a shift up/down indicator in order to achieve economic driving.

Works pretty well in my car, but struggles a bit to get the shift up/down points when going up a relatively steep incline. Sometimes it tells you to shift up, then notices labouring and tells you to shift down again.

It is good at getting me to shift down on inclines where I forget to notice the steepness incline and there isn't obvious labouring on the engine (usually when I've only shifted down from 5th into 4th when I should really have shifted all the way down to 3rd, even where speed is constant).

If you want to just stick to one gear for variable speed traffic then that is just being lazy imo.
 
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With an HGV it's much better fuel wise to let it lug down to the low part of its "green band" on the rev counter before changing down, yes it feels like it's labouring slightly but, it's what they do, they have huge torque and I often get better mpg when doing this - up to 1mpg improvement over a 400 mile trip - even though I don't maintain as much speed as I'd like.

With my little Corsa DTI I keep the thing above 1800rpm which seems to keep the turbo boosting and it seems to make little difference to mpg, I seem to get ~ 450 miles to a tank no matter how I drive the thing.
 
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