I have to say, I've tried the double de-clutching thing, and all I found it does is slow your progression up or down the gears. For 99% of the driving people do, I couldn't see the benefit. Unless you've lost the synch-mesh, or you're driving something pre-20's, or you're in something with straight cut gears for some reason.
I'm also told braking with the engine isn't as fuel efficient as using the brakes.

Double declutching isn't necessary with a modern car, but you should at least match the revs before changing up or down. Driving the car clutchless for a while and it will become second nature.

If you back off the throttle on a modern car, it doesn't use much/any fuel. If you brake and use the clutch the engine will, at best, idle, which uses more fuel... If you aren't dipping the clutch, then you are reducing speed more quickly than with engine braking, so, even if the fuel is cut, it doesn't run as long with fuel starving, so you won't reduce fuel consumption as much.

Engine braking - as in taking your foot off the throttle - should be much better for the car, it puts less stress on everything than waiting until the last moment and slamming the brakes on.

Heh, this just goes against what I was taught - if the car is out of gear, you're not in control of it properly.



I was also taught driving with the car in neutral for periods of time doesn't do the gearbox much good in the long term.
Any thoughts?



Indeed, but engine braking, to me, is using the gears and the engine's resistance to slow your speed, not just lifting off the go pedal.
I'm also reading that some ECUs, during a down shift (thus causing the revs to rise and the manifold pressure to change) cut the amount of fuel injected.

In fact, the more I read about this online, the more I think it entirely depends on the vintage of the car you're driving!

Only on automatics, AFAIK.

Edit: My grandfather was delivering lorries and cars to the military during the war, to save fuel, they'd slip into neutral and cut the engine when they hit a gradient. He was still doing that into the mid 80s, until he got a car with servo brakes (he'd then leave the engine on, but neutral) and then an automatic.


That is what you are doing, but you only slap it down a gear when you are a) almost at idle in the current gear or b) racing and braking hard and need the extra bit of assistance from the engine, in which case, you don't really give a stuff about longevity, as long as it will make it to the end of the race.

[/quote]In fact, the more I read about this online, the more I think it entirely depends on the vintage of the car you're driving![/quote]
I drive "enthusiastically" in my Mondeo (accelerate hard, cruise at between 85 and 90 on the autobahn, corner hard), but I still return well over 50mpg, because I tend to look ahead, especially on the autobahn, and if somebody is likely to pull out in front of me, I'll back off the throttle and use the engine braking to slow me down, so that I am almost at the same speed when I get up behind them, then I'm ready to step back on the throttle when the obstacle is out of the way. The same for changes in speed limit. I get off the throttle and let the engine breaking take me down from 85 to 50 for, say, roadworks.

The same on backroads, I'll usually let the engine do the braking coming into a village, coming down from 60 to 30. Judging the road condition, gradient etc. to see if I can actually hit 30 when I hit the village entrance sign.

A question for those people who say they don't use engine braking:

Say you were coming to a roundabout at the end of a fast road. Would you stay in top gear and use the clutch to stop you stalling, or would you change down through the gears as you slowed? At what revs/speeds would you change down?

I was thinking of this thread as I've been driving about recently, and in the car I have now I do need to gently use the brakes a little more often because the smaller petrol engine doesn't slow you down as much as the diesel I used to drive. I still lose most of my speed without braking though, and I rarely brake hard unless something very unusual and unexpected happens - usually involving an idiot.

Note, on the motorway I'll often touch the pedal when slowing just to put the brake lights on.

I'd use the brakes to slow until I reached the roundabout, leaving the car in top gear. What happens then depends on the traffic on the roundabout. If it's clear, drop down to an appropriate gear and continue. If not, dip the clutch, into neutral and wait. I've never used lower gears to slow a manual car down - that's not what they're meant for.

If you change down to a lower gear, and in the process cause the engine revs to rise, you're causing unnecessary strain on the clutch mechanism. This is particularly true of manual diesels that have dual-mass flywheels. These often cost more than a clutch to replace.

For the example given, I would first brake, dip the clutch as soon as it became necessary and at some point I would be able to decide whether I was actually going to need to stop or engage a gear appropriate to the speed. I would guess- and it is a guess, that the clutch would be down for two seconds max before I stopped or engaged another gear.

That pretty much sums up my thinking on this as well.

You should never be causing the revs to rise by the gear change itself! You should be dipping the clutch, blipping the throttle (or waiting for the revs to fall), until they are correct for the next gear, then let the clutch back out...

Anything I would add has pretty much been covered in the last four pages, but FWIW I use the brakes to slow down then select the appropriate gear accordingly.

This is the way I was taught to do it, unless driving in poor conditions on hills etc. where using the foot brake to slow down could be dangerous.

So you could be coasting for several seconds in the wrong gear?

I was taught that was dangerous, especially on a corner. I certainly wouldn't feel in control of the vehicle if I was in 5th gear at 30mph with my foot on the clutch



Changing down is surely no more "stress" than changing up, unless you're doing it very very wrong. You match the revs before letting up the clutch, and obviously you don't change into an inappropriate gear.

Just to remind everyone what Peter said:



40 in 3rd is hardly over-revving the engine, and as I've said repeatedly - changing from 4th to 3rd at 40mph is surely no more stressful than changing from 3rd to 4th at that speed. I'd concider that quite gentle driving in fact.

He did not say: "I'd change into 1st gear at 70mph, drop the clutch and rip the engine out the bonnet".

"So you could be coasting for several seconds in the wrong gear?

I was taught that was dangerous, especially on a corner. I certainly wouldn't feel in control of the vehicle if I was in 5th gear at 30mph with my foot on the clutch."

That isn't the case - coasting implies allowing the car to move with the clutch depressed and not in gear. I leave the car in gear until the car is about to come to a stop. Only at this point is the clutch depressed.

A corner is a different kettle of fish - how I approach a corner depends on a lot of factors such as visibility, sharpness, weather conditions, other road users, road layout etc. Only when all these have been taken into account can you decide which gear is appropriate and how the brakes/gears should be used.

"Changing down is surely no more "stress" than changing up, unless you're doing it very very wrong. You match the revs before letting up the clutch, and obviously you don't change into an inappropriate gear."

If you do it properly, that's true, but the vast majority of drivers don't - they just stick it in a lower gear and let the clutch out.