Why is it advised to depress the clutch on a car before starting the engine?

Question

Is it to do with letting fuel through? Also, why is it better to try and keep the revs low; does that make it more economical and environmentally friendly? Thanks.

Answer 1

clutch down makes no difference to anything...as for answers stating it guarantees the car wont jerk forward if its left in gear...driving test requires its left in neutral,also requires u to check its in neutral before starting...low revs can cause more fuel consumption as you labour the engine [more co2],actually best is a lower gear and slightly higher revs,,,its been proven.

Answer 2

1..most cars today will not start without pushing in clutch

2..its a safty thing

3..the engine turns/starts  easier without the clutch turning..

Answer 3

Depressing the clutch makes it easier to start the car. Even with the car in neutral the engines starter motor still has to crank the engine and the gearbox. However if you depress the clutch before (and during) starting the gearbox is removed from the equation & all the starter motor has to do is crank the engine. This reduces wear on the components & makes it easy to start.

Low revs:

Every car has a tradeoff between efficiency & speed for both motorways and urban driving. On the average petrol car the most efficient point is around 55 - 60 miles per hour and around 2500rpm. This is the point where the car is using the least amount of fuel for every mile travelled. Travelling at lower revs at a slower speed is more economical on fuel but increases the strain on the engine and gearbox. Travelling at faster speeds and higher revs also increases the wear & tear of the engine and gearbox components but makes the car less fuel efficient as the engine has to work harder to overcome wind resistance etc. Obviously during the urban cycle cars also have a different point where they are most fuel efficient this is usually around 30mph in 4th gear.

It is a common misconception however that travelling slower is more fuel efficient & environmentally friendly as travelling at 25mph in third or fourth is less fuel efficient than travelling at 60mph in 5th or 6th. The most efficient way to use a car is to accelerate to a given speed, gently & then try to stay at that steady speed.  

Answer 4

In the early days when cold lubricants were quite sticky it disconnected the transmission drag (even in neutral there was some) from the starter motor. Nowadays it's just a sensible safety precaution in case the car's in gear

Answer 5

Hi Hun, I would imagine to make sure it is not left in gear, as for the revs it makes economical sense.

I drive both a manual and an auto, I dip the clutch even when I don't have one! lol!

Answer 6

2 reasons

1 to disengage the drive system so the vehicle will not move in any direction Clutch in no gear mesh to drive either forward or reverse.

(remember the hand brake should be on and your other foot should be on the foot brake while starting the car)

2 Some (most late model) cars have a cut out switch installed (for safety) and you must depress the clutch which then allows current to reach the starter motor so it will start the car.

This system is much like the automatic cut out switch of automatic transmission cars and I believe the idea came from automatic transmission cars.

Keeping the revs low? when, why?

I guess if you are at idle and about to start to drive off the engine should not "race" or rev up high as this can cause damage to the engine as with most things gentle touch is much less intrusive I need you to explain what is meant by low revs in what circumstance or context was it said to you?

Hope this answered your question for you Happy safe driving

Answer 7

It is to take load from the starter motor by disengaging the gearbox.

The down side of doing this is that your loading the clutch release bearing and putting your clutch through one unnecessary cycle. The big downside that is always overlooked is that you loading the crankshaft thrust washers when they have just minimal lubrication.

Modern gearbox lubricants make this practice outdated, when starting just make sure that your in neutral.

If your concerned about your starter motor rember they're easier and cheaper to replace than a clutch or a crankshaft.

Answer 8

I have never been advised to press the clutch while starting, and never do. So, it has nothing to do with fuel. The driving test says always check that you are in neutral before starting, so it has nothing to do with being in gear. A drain on the battery because you are turning over the gearbox as well as the engine, hang on, you're in neutral. Keep the engine at low revs, Oh! Yes! make the engine labour and hunt, damaging the clutch and engine mounts.

I usually keep my revs above about 3 thousand, and use the appropriate gear.

Answer 9

You only need to depress the clutch if the vehicle is in gear, this stops you stalling and the vehicle jumping forward which is what would happen if you started the car in gear. Also, yes it is a good idea when driving, to keep the revs down, as it helps reduce fuel consumption and can reduce excessive wear and tear.

Answer 10

Depress the clutch to prevent the starter motor from moving the car (old style) most newer cars have a lockout switch to prevent starting with clutch out. Fuel has nothing to do with it.

Answer 11

Depress th clutch before starting for safety, just in case it is engaged in gear, so will not shoot forwards or backwards.

Yes more economical on fuel keeping revs low.

Answer 12

Safety, if the vehicle is left in gear then then it won't lurch forward or reverse.  Many people whom are accustomed to driving an automatic vehicle would not think to check it the vehicle was in gear before starting.

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Answer 13

depress the clutch to keep car from taking off first and it take off pressure from the motor making it easier to start

Answer 14

if u dont press the clutch and ur car is in gear it will lurch 4ward and hit the car in front. if u put full revs on u might set off too quickly and possibly lose control. hope ive been some help

Answer 15

The main reason for declutching when starting is to reduce the load on the starter motor and battery, particularly in an older car. The reason is that the starter only has to turn the engine over and not the gearbox which when cold can be quite stiff due to the heavier oil in a gearbox, particularly on a cold morning.  

Answer 16

A couple of possibilities:

- The car may have been mistakenly left in gear

- It ensures that the gears are 100% disengaged and so takes some strain off the starter motor  

Answer 17

common sense if it has been left in gear it will save you a repair bill for hitting the garage wall

Answer 18

Depressing the clutch was recommended on older cars, to help relieve the load on the starter from a cold and sticky gearbox (there still is some drag, even in neutral). It's nothing to do with starting in gear, after all you learn to check the handbrake is on and the gears are in neutral before you attempt to start, don't you? It's unnecessary these days, unless there happens to be a cut-out on your car which won't allow the starter to work unless the clutch pedal is down.

Regarding the engine revs, all you need to do is avoid excessively high revs or, for that matter, excessively low revs.  The idea is to be gentle on your engine, neither flogging it nor making it struggle, and that leads to better fuel consumption too.  Probably somewhere in the mid-2,000s revs is best, but don't focus on that to the extent that you become a danger to yourself or other road users.  The engine will rev up to at least the yellow line, so use it if you need to.

Answer 19

Stop the car lurching forwards if it is in gear, and also the starter-motor is working hard enough as it is, turning the flywheel and the heavy crank in the engine, without asking it to spin the gearbox and prop-shaft up to speed as well!

Answer 20

Most makers recommend depressing the clutch to reduce wear on the starter motor by disconnecting the gearbox from the engine, in reality it doesn't make any difference, and it's cheaper & easier to replace a starter motor than a clutch release bearing.

Keeping the revs low (but not so low that the engine struggles) reduces engine wear & improves economy and reduces emissions.