Does down shifting reduce you gas mileage? Is it better to coast in neutral and then apply brakes or to anticipate the stop point with engine braking?

 

No idea, but it typically extends the rotor and pad life by triple that of any automatic version. That alone will save you more money than the negligible extra amount of gas it uses.

 

Engine Braking does not waste anymore gas than coasting, it does make you come to a stop faster. Engine Braking works on the compression, so unless you gas it while you are engine breaking then it won't waste anymore gas than when you are coasting.

 

engine braking uses MUCH less gas than simply putting the car in neutral. i assume you're talking about a manual transmission.

even leaving the car in fifth on a downhill on the freeway, is better than putting it in neutral.

 

Fuel is in fact cut when coasting in gear, as long as the engine speed is above 1500rpm (MT) or 1000rpm (AT).

Coasting in neutral causes the engine to idle - which burns gas.

Thusly, coasting in gear is more efficient.

 

FASing is even better......it wastes no fuel and causes you to not want to use your brakes by wanting to get the most out of your coasting.

 

Um.... yeah because turning off the car as you come to a stop (resulting in loss of power steering and power assisted brakes) isn't just horribly dangerous, it is also annoying to other drivers who would rather just travel the speed limit. The larger fact being that if you need to come to an abrupt stop you have compromised your car and risk plowing into somebody, so in affect you are endangering the health and possibly life of not only yourself but drivers, passengers and pedestrians around you.

~End Rant~

Sorry, no disrespect meant here. I am of the opinion that people should consider other drivers around them. People that slow down a block before and then take 3 city blocks to get to a reasonable speed infuriate me. If I catch anyone doing this FASing technique in a busy area I will take their plate number down and report them for dangerous driving.

Somebody want to verify this with a scangauge. I would be interested in seeing the results. I suspect when you engine brake the engine uses less fuel or the same as coasting.

 

Let's put it this way.

1) Engine braking puts unnecessary load on the engine. (OK, so I was wrong, fuel is nearly to completely cut off)

2) Coasting in neutral and applying the brakes causes no unnecessary wear on the engine or any part of the car except for the brakes pads (which are readily replaceable) and little to no wear on the rotors.

It all boils down to cost. Would you rather buy and replace brake pads (and occasionally rotors, if need be) or unnecessarily worn engine components? If your pockets are deep, then be my guest to do the latter.

I can already tell you that coasting in neutral uses less fuel. Let's say you want to slow from 30mph to 10mph using both methods and, for the sake of simplicity, it takes equal amounts of time t to do so. Also, acceleration is constant. (RPMs are also hypothetical, used only as an example)
If engine braking, then the engine starts at 2000 rpm and decreases until it reaches 1000 rpm over that time interval t.
If coasting, then the engine is at a steady 900 rpm (that's what my car idles at) over the entire time interval t.
Logically, coasting is going to use less fuel. (and if you wanted, you could use gal/hr instead of rpm; either way, same result)

 

1) slowing the car by engine braking puts no more load on the engine than does accelerating. The process is just reverse: the wheels turn the transmission which turns the engine. It has been VERIFIED with a ScanGauge that there is IN FACT no fuel being injected during this condition (above engine stall speed) I just got my ScanGauge today, and have already seen and verified this behavior.

2) true that coasting in neutral should cause no additional wear to your engine. It will cause your brakes to wear more, and also leaves the engine idling.

 

Disadvantages:
"Engine braking beyond normal engine drag (i.e., shifting the vehicle into a different gear to slow it down) transfers wear and tear to parts that are typically the most expensive and difficult to replace, including but not limited to the engine, transmission, clutch, etc. Traditional braking puts most wear and tear on parts that are an order of magnitude easier and less costly to replace: brakes and rotors."

I'd much rather replace my brake pads than parts of my engine.

Also, a lot of cities and states have laws prohibiting engine braking because of noise ordinances.

 

That is pretty much what I figured; as for the second point you could debate engine life VS brake pads to death without a real result.

What I can say is in my own experience I always engine brake in my daily driving, my last set of pads only lost 15% over 60,000km. I can't directly attribute any engine wear problems on any cars I have owned to the use of engine brakes. Everything seems to wear out at a pretty normal rate.

I think this is only for big rigs. Lots of them even have engine brakes on automatic vehicle's.

 

It's not limited to just big rigs, though.

"Compression braking, a form of engine braking, produces extreme amounts of noise pollution if there is no muffler on the intake manifold of the engine. Use of an exhaust brake produces similar effects, due to release of compressed gasses, but the mechanism is distinct from regular car engine braking. Anecdotally, it sounds similar to a jackhammer, however the loudness is between 10-20 times the sound pressure level of a jackhammer. Numerous cities, municipalities, states, and provinces have banned the use of unmuffled compression brakes.
This is often a source of dissatisfaction to professional truck drivers, some of whom believe that municipalities are taking advantage of them due to their transient nature, and thus disregard the law, believing that they will be gone before a complaint can be lodged."

 

I have noticed that when you down shift the fuel starts to flow again and than turns off. Based on that, I try to stay in 5th or 4th (till I'm almost stopped and press the clutch) if I want to eng brake. My info is from watching SG fuel flow observations.

 

I must dispel these myths of FASing you speak of:

- power steering is not necessary and is only useful and noticeable when driving very slow like when parking, therefore it does not affect your driving at moderate speeds

- power brakes- you have at least 3 good brake pushes left and the rest requires pushing on the brakes harder. Now, this would be the factor to worry about but one can over come this by practice and knowing your car



Now, for being considerate of other drivers..............the speed limit is just that a limit. You should not go over the speed limit(hence tickets). However, one should take warning when a speed range is given lets say on the interstate it is 45-60mph, then stay in that range(which is what I do......I can't speak for others). Also, your local or state laws may have a minimum speed limit for any maximum speed limit posted, be aware of that. Speeders are the ones who are not considerate of other drivers for they are in a hurry and are concerned for them selfs, hence speeding. If speeders were concerned about other drivers then they would not endanger themselves and/or passengers and other drivers by driving over the speed limit.

 

I think that is specific to the j-brakes on diesels, gearing down with a gasoline engine doesn't produce that much noise. I am pretty sure that my car is louder when I accelerate than when I gear down for sure!

Jake brake - Wikipedia, the free encyclopedia

 

I personally don't speed, I don't have any tickets over a span of about 10 years. What gets to me is the traffic lights downtown (at least where I live) the traffic lights are specifically synchronized to traffic doing the speed limit. Somebody that doesn't travel at the speed limit or spends 3 blocks gaining speed he/she will encounter several more traffic lights as a result and imped traffic behind them. All I ask is that people accelerate and decelerate at a reasonable speed.

Anything that impairs your cars ability to stop quickly is adversely impacting the safety. What if you need more than 3 good pumps? What if a person on a bike cuts in front of you and you can't react fast enough because your power steering is gone. These may seem like little details, but it may be enough to cause an accident. Is it really worth the extra mileage. I respect you guys doing what you can to maximize your fuel but the line needs to be drawn when safety gets compromised.

NOTE: Anyway, I don't want to get too one sided on this issue. I do like to keep an open mind; Has anybody done testing to see how a car that has been turned off reacts in emergency maneuvers should they arise? What about insurance company policies regarding this technique? Differences in braking distance?

 

The above quote indicates wearing by actually DOWNSHIFTING, not by coasting. You WILL put more wear on your clutch (in a manual) if you DOWNSHIFT to slow. Oh, and a quote isn't worth crap unless you cite it's source.

You WILL NOT cause drastic wear if you just lift off the throttle and leave the transmission in gear.

And about the city ordinance - be glad we're driving Fits, not diesel tractor trailers.