Preserving clutch and gas mileage

[TheLonelyPhoenix]

I just bought my first car, a Mazda3s with manual transmission. As I had been learning to drive manual transmission on my father's BMW 5-series, switching to my car changed things up quite a bit for me (going from a well-worn clutch with rear-wheel drive and massive torque to a brand-new clutch with front-wheel drive and moderate torque). In addition to quickly adapting my driving habits, I'm not too familiar with the different driving techniques I can use with a stick shift to preserve my gas mileage as long as possible and avoid wearing down my clutch (and brake pads). In particular, I'd like to know more about:

-Double-clutching (how its done, and what its benefits are)
-Engine braking (downshifting to slow down instead of using the brakes)
-Ideal engine RPMs and shift speeds

Any info on these topics (or any others pertaining to keeping my car running in good shape for as long as possible) would be greatly appreciated. Thanks in advance

 

[HappyPuppy]

Manual trannys from long ago didn't have synchros and double clutching was used to keep from grinding gears. Modern manuals have synchros and don't require double clutching except, possibly, in some racing situations.

 

[Amorphus]

Google can help!

 

[GTaudiophile]

Ehhh, lots of things to say I guess:

1) Don't rev your car over 3500-4000 rpm until it's warm.
2) Never ride the clutch. When you stop anywhere, put the car in neutral, let out the clutch, and take your foot off the clutch.
3) Don't race. AKA, don't drop the clutch at high revs.
4) Learn to make gear changes as smooth as possible, no lurching or slipping. It's not just clutch in, gear change, clutch out, add gas. It's more clutch in, fast shift, clutch out slowly while slightly adding gas at the same time.
5) Double-clutching: Clutch in, shift to neutral, clutch out, clutch in, shift into gear, clutch out slowly while adding a little gas.
6) Engine breaking is simply downshifting without adding gas as you approach a stop. Just NEVER downshift at a point that will cause you to redline.
7) NEVER ride with your foot on the clutch.

 

[episodic]

If you are real good you can put it in without a clutch (at least I could on my cj-5 way back). . .
Course I never used a clutch when I drove a semi either . . .
Float the gears . . . be one with the engine

 

[TheLonelyPhoenix]

Originally posted by: GTaudiophile
Ehhh, lots of things to say I guess:

1) Don't rev your car over 3500-4000 rpm until it's warm.
2) Never ride the clutch. When you stop anywhere, put the car in neutral, let out the clutch, and take your foot off the clutch.
3) Don't race. AKA, don't drop the clutch at high revs.
4) Learn to make gear changes as smooth as possible, no lurching or slipping. It's not just clutch in, gear change, clutch out, add gas. It's more clutch in, fast shift, clutch out slowly while slightly adding gas at the same time.
5) Double-clutching: Clutch in, shift to neutral, clutch out, clutch in, shift into gear, clutch out slowly while adding a little gas.
6) Engine breaking is simply downshifting without adding gas as you approach a stop. Just NEVER downshift at a point that will cause you to redline.
7) NEVER ride with your foot on the clutch.

How long should it take me to get my foot off the clutch while getting moving from a dead stop? Or when changing gears while normally shifting or double-clutching? Those are the times I get most nervous that I'm putting undue wear and tear on my clutch.

Also, I'm not quite sure when it is while double-clutching that I'm supposed to re-engage the gear.... is the idea to wait for the RPMs to drop to exactly where a higher gear needs them, then engage the gear while applying gas to keep the RPMs there while the clutch is going out? That's how I understand it, at least.

As for Google... lots of info about powerbands and racing tips, not so much on everyday driving techniques. Besides, I want info that comes from real people who have tried and tested the info they hand out. That is, after all, why ATOT rocks

 

[MisterMe]

If the life of your clutch is of importance to you then consider not engine breaking. On the contrary, as you knwo you will be coasting to a stop, let off the gas and at the very same moment you can sift out of gear without using the clutch. Over the lifetime of the clutch, imagine how many times this will have avoided wear that would have otherwise occurred.

OR...maybe you can forget about economizing on a component that is designed to wear out anyway and sock an additional $5 a month away for its eventual replacmenet cost. 75,000 miles out of a clutch at 12,000 miles a year would give you about $375 to hand over to your transmission guy....

 

[Zenmervolt]

Originally posted by: TheLonelyPhoenix
Also, I'm not quite sure when it is while double-clutching that I'm supposed to re-engage the gear.... is the idea to wait for the RPMs to drop to exactly where a higher gear needs them, then engage the gear while applying gas to keep the RPMs there while the clutch is going out? That's how I understand it, at least.

Double clutching is an advanced technique that should be avoided until after you have become proficient at regular shifting. No modern automotive transmissions require double-clutching.

ZV

 

[Zenmervolt]

Originally posted by: MisterMe
If the life of your clutch is of importance to you then consider not engine breaking. On the contrary, as you knwo you will be coasting to a stop, let off the gas and at the very same moment you can sift out of gear without using the clutch. Over the lifetime of the clutch, imagine how many times this will have avoided wear that would have otherwise occurred.

OR...maybe you can forget about economizing on a component that is designed to wear out anyway and sock an additional $5 a month away for its eventual replacmenet cost. 75,000 miles out of a clutch at 12,000 miles a year would give you about $375 to hand over to your transmission guy....

Engine braking does not wear the clutch at all. It causes no slippage. Properly done, one should hold whatever gear he was in with the clutch engaged and leave the clutch engaged until just above idle, at which point he should disengage the clutch, select neutral, and use the brakes alone to complete the stop.

Pulling the transmission out of gear when there is a load on it (i.e. acceleration or deceleration) places large stresses on the shift forks and will accelerate transmission wear. Unless you are extremely proficient at matching revs, you should not even think about selecting or de-selecting any gear without first disengaging the clutch.

ZV

 

[m2kewl]

Originally posted by: Zenmervolt

Originally posted by: TheLonelyPhoenix
Also, I'm not quite sure when it is while double-clutching that I'm supposed to re-engage the gear.... is the idea to wait for the RPMs to drop to exactly where a higher gear needs them, then engage the gear while applying gas to keep the RPMs there while the clutch is going out? That's how I understand it, at least.

Double clutching is an advanced technique that should be avoided until after you have become proficient at regular shifting. No modern automotive transmissions require double-clutching.

ZV

agreed. also don't try this on the streets/highway if you're a n00b...results can be major property damage and/or hospital visit

 

[GTaudiophile]

Rev-matching is part of double-clutching. It's an art, but you can figure it out.

I'll discuss more later.

 

[Zenmervolt]

Originally posted by: m2kewl

Originally posted by: Zenmervolt

Originally posted by: TheLonelyPhoenix
Also, I'm not quite sure when it is while double-clutching that I'm supposed to re-engage the gear.... is the idea to wait for the RPMs to drop to exactly where a higher gear needs them, then engage the gear while applying gas to keep the RPMs there while the clutch is going out? That's how I understand it, at least.

Double clutching is an advanced technique that should be avoided until after you have become proficient at regular shifting. No modern automotive transmissions require double-clutching.

ZV

agreed. also don't try this on the streets/highway if you're a n00b...results can be major property damage and/or hospital visit

I remember back when I first was trying double clutching. I focused so much on the footwork that I once forgot to shift... That was a trifle surprising to come off a slow corner and think I was shifting into 3rd but instead only re-engaging 2nd...

ZV

 

[MisterMe]

Pulling the transmission out of gear when there is a load on it (i.e. acceleration or deceleration) places large stresses on the shift forks and will accelerate transmission wear. Unless you are extremely proficient at matching revs, you should not even think about selecting or de-selecting any gear without first disengaging the clutch.

Hmmmm - not quite what the guys at my Skip Barber class told us about the situation. Of course under acceleration or deceleration there is load on the gears - don't shift at that point. But we were told that if at the same moment you let off the gas to coast to the stop, the engine transitions from load to unloaded and it's at this exact point that de-selecting the gear to neutral would incur no wear on the clutch or drivetrain as a whole. Try it to see what I'm talking about. I myself will put a slight pressure towards neutral while still under power and the moment I let off the gas, the shifter almost magically slips into neutral...

Also the engine breaking does not necesarily wear the clutch by itself but think about whats happening here. If you're coasting to a stop, shifting into the next lower gear WILL ADD an otherwise uneeded level of friction wear to the clutch and maybe more appropriate for this topic, additional engine revs and therefore more fuel consumption....

 

[TheLonelyPhoenix]

Originally posted by: Zenmervolt

Originally posted by: MisterMe
If the life of your clutch is of importance to you then consider not engine breaking. On the contrary, as you knwo you will be coasting to a stop, let off the gas and at the very same moment you can sift out of gear without using the clutch. Over the lifetime of the clutch, imagine how many times this will have avoided wear that would have otherwise occurred.

OR...maybe you can forget about economizing on a component that is designed to wear out anyway and sock an additional $5 a month away for its eventual replacmenet cost. 75,000 miles out of a clutch at 12,000 miles a year would give you about $375 to hand over to your transmission guy....

Engine braking does not wear the clutch at all. It causes no slippage. Properly done, one should hold whatever gear he was in with the clutch engaged and leave the clutch engaged until just above idle, at which point he should disengage the clutch, select neutral, and use the brakes alone to complete the stop.

Pulling the transmission out of gear when there is a load on it (i.e. acceleration or deceleration) places large stresses on the shift forks and will accelerate transmission wear. Unless you are extremely proficient at matching revs, you should not even think about selecting or de-selecting any gear without first disengaging the clutch.

ZV

So you're not supposed to switch gears when engine braking, but simply use the internal resistance of the gear you're in to decelerate? Doesn't that make it almost pointless in the higher gears? (4th and up)

I'm decent at normal gear selection, can switch between each gear with very little jerk in the car and virtually none past 3rd gear... however, I think I'm still taking too long getting my foot off the damn clutch pedal, especially going into first from a stop. How long should it take me to make each transition?

 

[Zenmervolt]

Originally posted by: MisterMe

Pulling the transmission out of gear when there is a load on it (i.e. acceleration or deceleration) places large stresses on the shift forks and will accelerate transmission wear. Unless you are extremely proficient at matching revs, you should not even think about selecting or de-selecting any gear without first disengaging the clutch.

Hmmmm - not quite what the guys at my Skip Barber class told us about the situation. Of course under acceleration or deceleration there is load on the gears - don't shift at that point. But we were told that if at the same moment you let off the gas to coast to the stop, the engine transitions from load to unloaded and it's at this exact point that de-selecting the gear to neutral would incur no wear on the clutch or drivetrain as a whole. Try it to see what I'm talking about. I myself will put a slight pressure towards neutral while still under power and the moment I let off the gas, the shifter almost magically slips into neutral...

Also the engine breaking does not necesarily wear the clutch by itself but think about whats happening here. If you're coasting to a stop, shifting into the next lower gear WILL ADD an otherwise uneeded level of friction wear to the clutch and maybe more appropriate for this topic, additional engine revs and therefore more fuel consumption....

You'll note that I specified only when there is load on the transmission. I know bloody well what you're talking about. But this person is a shifting newbie. He's not going to be able to consistantly identify that point and he should not be attempting those kinds of things without being proficient in the basics first. It's inviting problems.

You'll also note that I specified in my post (though you chose not to quote that part) that I was talking about staying in whatever gear was previously selected and that I implicitly excluded the possibility of shifting through the gears individually, which would naturally wear the clutch minimally.

Finally, regarding fuel consumption, revs do not equal fuel consumption, unless you are somehow finding a brand new carburetored car. On _all_ modern fuel injection systems (e.g. any EFI system since the 1980's) senses an engine braking scenario and shuts off the injectors, making the engine into one big compression brake. There is actually less (as in, zero) fuel consumption under engine-braking scenarios than there is when the engine is at idle because of this.

ZV

 

[MisterMe]

Originally posted by: TheLonelyPhoenix
So you're not supposed to switch gears when engine braking, but simply use the internal resistance of the gear you're in to decelerate? Doesn't that make it almost pointless in the higher gears? (4th and up)

I'm decent at normal gear selection, can switch between each gear with very little jerk in the car and virtually none past 3rd gear... however, I think I'm still taking too long getting my foot off the damn clutch pedal, especially going into first from a stop. How long should it take me to make each transition?

Engine breaking is using the natural tendency of the lower gear to rve the engine up to the appropriate rpm to match the speed. Say if you're going 40 in third, 2500 rpm, and you use engine breaking, shifting into 2nd would make the engine rev to 4500. The difference in the time it takes for the engine to rev to it's natural speed/rpm level is what causes the car to effectively slow down...keep it in second without the gas and you could do it again shifting into 1st when the speed would allow rpms to stay at a safe level.

What I saying is in efforts to "save your car" you might avoid engine breaking an coast to stops. Doing this avoids the rpm spikes and save you gas.

Sounds like you're new to the sticks and because that, don't worry about it too much. Know that you will get to the point where upshifts are completely smooth...it's just a matter of time. As for the time it takes? I don't know but if you're aggressively driving the thing than I'd say less than a second. If you're just cruising to the grocery store, I wouldn't worry if it takes you 3-5 seconds to leisurely go from one gear to the next....it doesn't always have to be fast...

 

[Zenmervolt]

Originally posted by: MisterMe
What I saying is in efforts to "save your car" you might avoid engine breaking an coast to stops. Doing this avoids the rpm spikes and save you gas.

No, it does not. It uses more gas to coast. I went over that in my last post. All modern electronic fuel injection systems detect engine braking and turn off the injectors down to a specified RPM cutoff (typically 100-200 RPM above idle) at which point idle-level fuel-flow is restored. This means that exactly zero fuel is used during engine braking (until the threshold RPM is reached, at which point only idle levels of fuel are consumed), whereas coasting down uses an idle-level of fuel during the entire slowdown period as opposed to just at the end.

ZV

 

[Eli]

Listen to ZV, he knows his sh!t.

 

[TheLonelyPhoenix]

Okay, so what kind of techniques should I be using now in the interests of not wearing down my clutch or burning up too much gas, and what should I learn about for future reference once I'm proficient at normal shifting?

And last I checked, replacing a front wheel drive clutch was about $800+, so I do believe its a good component to economize.

 

[acemcmac]

Originally posted by: Zenmervolt

Originally posted by: MisterMe
What I saying is in efforts to "save your car" you might avoid engine breaking an coast to stops. Doing this avoids the rpm spikes and save you gas.

No, it does not. It uses more gas to coast. I went over that in my last post. All modern electronic fuel injection systems detect engine braking and turn off the injectors down to a specified RPM cutoff (typically 100-200 RPM above idle) at which point idle-level fuel-flow is restored. This means that exactly zero fuel is used during engine braking (until the threshold RPM is reached, at which point only idle levels of fuel are consumed), whereas coasting down uses an idle-level of fuel during the entire slowdown period as opposed to just at the end.

ZV

which gas got to be like amost no gas at all either way, right?

 

[Eli]

Originally posted by: TheLonelyPhoenix
Okay, so what kind of techniques should I be using now in the interests of not wearing down my clutch or burning up too much gas, and what should I learn about for future reference once I'm proficient at normal shifting?

And last I checked, replacing a front wheel drive clutch was about $800+, so I do believe its a good component to economize.

If you're conciously making an effort to avoid as much slip as possible, the clutch wearing out is not something you'll need to worry about, unless it is a used car and close to being worn out anyway.

A new clutch could last the life of the car if the user is very gentle(ie: 200,000 miles).

 

Originally posted by: Zenmervolt

Originally posted by: MisterMe
What I saying is in efforts to "save your car" you might avoid engine breaking an coast to stops. Doing this avoids the rpm spikes and save you gas.

No, it does not. It uses more gas to coast. I went over that in my last post. All modern electronic fuel injection systems detect engine braking and turn off the injectors down to a specified RPM cutoff (typically 100-200 RPM above idle) at which point idle-level fuel-flow is restored. This means that exactly zero fuel is used during engine braking (until the threshold RPM is reached, at which point only idle levels of fuel are consumed), whereas coasting down uses an idle-level of fuel during the entire slowdown period as opposed to just at the end.

ZV

Yup, I've felt that on my honda before. When I get down to a low enough speed, I feel a noticable 'bump' and the RPMs drop to about 200. It's really nice, cause if hte light turns green, I can just gas and go, or if I need to accelerate faster, I can just downshift and go.

Engine braking in the CURRENT gear is the way to go. Anything else, IMHO will simply wear the clutch if you don't do it perfectly.

 

[Zenmervolt]

Originally posted by: TheLonelyPhoenix
Okay, so what kind of techniques should I be using now in the interests of not wearing down my clutch or burning up too much gas, and what should I learn about for future reference once I'm proficient at normal shifting?

And last I checked, replacing a front wheel drive clutch was about $800+, so I do believe its a good component to economize.

The fuel consumption amount is academic. While you technically save fuel by engine braking, it's not enough to make any measurable difference in the real world. Remember that an idling engine burns something like 1 gallon of fuel every two hours. So if your engine is idling and you're coasting at 60mph, you're effectively getting 120 mpg at that instant. It's not enough to worry about.

As for techniques:

Keep your foot off the clutch unless you want it completely disengaged. Unless you are changing gears or sitting in neutral/starting off you should never rest your foot on the clutch pedal.

When shifting, press the clutch pedal to the floor and move the leave smoothly to the next gate. Do not try to rush things, just make it smooth for now. Speed will come later on its own. Be sure to engage and disengage the clutch smoothly too, again, speed will come in time on its own.

Honestly, there is nothing that you need to learn beyond normal shifting. Double-clutching is kinda fun, but it increases wear on the clutch, and it's purely un-necessary as long as you're not a race driver.

I stand by my recommendation to leave the car in gear when braking until 1,000 RPM (or slightly higher), then going to neutral and completing the stop. That doesn't wear the clutch because you're not shifting and it does capture some benefit of engine braking.

ZV

 

[Zenmervolt]

Originally posted by: acemcmac

Originally posted by: Zenmervolt

Originally posted by: MisterMe
What I saying is in efforts to "save your car" you might avoid engine breaking an coast to stops. Doing this avoids the rpm spikes and save you gas.

No, it does not. It uses more gas to coast. I went over that in my last post. All modern electronic fuel injection systems detect engine braking and turn off the injectors down to a specified RPM cutoff (typically 100-200 RPM above idle) at which point idle-level fuel-flow is restored. This means that exactly zero fuel is used during engine braking (until the threshold RPM is reached, at which point only idle levels of fuel are consumed), whereas coasting down uses an idle-level of fuel during the entire slowdown period as opposed to just at the end.

ZV

which has got to be like amost no gas at all either way, right?

Yes, but it's still more fuel than engine braking. I'm trying to dispel the all-too-common myth that engine braking uses more fuel.

ZV

 

[MisterMe]

Originally posted by: Zenmervolt

Originally posted by: MisterMe
What I saying is in efforts to "save your car" you might avoid engine breaking an coast to stops. Doing this avoids the rpm spikes and save you gas.

No, it does not. It uses more gas to coast. I went over that in my last post. All modern electronic fuel injection systems detect engine braking and turn off the injectors down to a specified RPM cutoff (typically 100-200 RPM above idle) at which point idle-level fuel-flow is restored. This means that exactly zero fuel is used during engine braking (until the threshold RPM is reached, at which point only idle levels of fuel are consumed), whereas coasting down uses an idle-level of fuel during the entire slowdown period as opposed to just at the end.

So if this kid is trying to save his car to the utmost extent, which way would you tell him to avoid the most wear and tear over the lifespan of a clutch/engine?