Is it mechanically safe to coast in neutral?

Will it damage the transmission/engine to re-engage into Drive from Neutral when the car is in motion? or into Neutral from Drive mode? Does coasting in Neutral saves gas? similarly will it help the transmission/engine when the car is in Neutral instead of Drive while stopping (at signals etc).

Is it better to stop the engine when waiting on signals or should we keep the engine running? When is it advisable to shut the engine (say waiting for more than 30 seconds/45 or more than that). Will frequent start and stop hurt the engine/ starter more than it would save the gas or prevent engine wear

Experienced mechanics share their insights in answering this question :
Technically, least cost operation is attained if engine idling (at stops) does not exceed 60 seconds and, indeed, some studies put the threshold as low as 10 seconds. Certainly 60 seconds is a conservative estimate. This is why "start-stop" features on modern engines have become popular; "start-stop" saves money. As a practical, and most importantly safety matter though, unless your vehicle came equipped from the factory with start-stop technology, do NOT turn your vehicle off at intersections because that practice will substantially increase the risk of a collision and has the potential to impede traffic flow as you attempt to mimic the operation of what is ordinarily seamless start-stop technology. In all other settings, though, as noted if your vehicle is sitting idle for as little as 10 seconds you will save money turning the vehicle engine off. As far as shifting from drive to neutral and back again, although there is no damaging effect in an automatic transmission, such a practice is NOT recommended, again due to the safety hazard such a practice creates. During these periods when the transmission is in neutral, you have no ability to accelerate the car, if it becomes necessary to avoid a collision. You also loose all engine braking, there is no appreciable gas savings, and the manual shifting becomes a driver distraction. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

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Unfortunately not – Coasting can be dangerous and coasting doesn`t save fuel. If you`re new to driving and are reading this, coasting is when you drive along with the clutch pushed in, or have the gear stick in neutral – or both. This disengages the engine from the wheels.
Coasting has no real affect on the internal mechanics of your car. However, it does lead to the overuse of one clutch component in particular for manual cars: the throw out bearing. The throw out bearing is the part of the clutch system that disengages the engine while the clutch pedal is pressed.
In the vast majority of modern cars with electronic fuel injection, Engineering Explained reveals that it is more fuel efficient to coast in gear than in neutral.
A: That depends. The engine isn`t braking the car going downhill if the transmission is in Neutral, so economy would seem to be high. But if you think the engine is still using fuel while coasting downhill in gear, you`re laboring under a misconception.
Don`t Coast With It in Neutral

You put the shifter into the “neutral” position and your thinking is that you save fuel by not having any load on the engine. That`s wrong thinking. Modern vehicles actually don`t use any fuel when coasting and in “drive” (or in a gear in the case of a manual transmission).

All cars are designed to start at the lowest gear, as that`s where you get the most power for acceleration, but driving at the highest gear will increase fuel economy. Fuel consumption will increase when you stay long at lower gears.
There`s a rare occasion where you might leave the car in neutral. That`s when you`re in an absolutely flat parking space and there are cars ahead of you and behind you. If one of the cars hits you when it goes to pull out, there`s less stress on your transmission if your clutch is disengaged.
Never leave your car in neutral when parked.

Well, the manuals are deprived of the park, so do we have to leave the car in neutral? Absolutely not, like the park in automatic, one should always engage either the first gear or reverse gear along with the parking brake (Especially when parking on slopes).

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

Is it mechanically safe to coast in neutral?
ANSWER : Technically, least cost operation is attained if engine idling (at stops) does not exceed 60 seconds and, indeed, some studies put the threshold as low as 10 seconds. Certainly 60 seconds is a conservative estimate. This is why "start-stop" features on modern engines have become popular; "start-stop" saves money. As a practical, and most importantly safety matter though, unless your vehicle came equipped from the factory with start-stop technology, do NOT turn your vehicle off at intersections because that practice will substantially increase the risk of a collision and has the potential to impede traffic flow as you attempt to mimic the operation of what is ordinarily seamless start-stop technology. In all other settings, though, as noted if your vehicle is sitting idle for as little as 10 seconds you will save money turning the vehicle engine off. As far as shifting from drive to neutral and back again, although there is no damaging effect in an automatic transmission, such a practice is NOT recommended, again due to the safety hazard such a practice creates. During these periods when the transmission is in neutral, you have no ability to accelerate the car, if it becomes necessary to avoid a collision. You also loose all engine braking, there is no appreciable gas savings, and the manual shifting becomes a driver distraction. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

Motor mounts. Which mechanic is right?
ANSWER : If a motor mount diagnostic was performed and the mounts were confirmed to be faulty, the only safe repair strategy would have been to install dealer OEM motor mounts. If you use aftermarket parts in this application in essence you are using your time, money, and so forth to conduct an experiment with parts that, very often (not always, but VERY often) simply were not designed for your car. As a practical matter, the only way to determine if new motor mounts will resolve your issue is to install the mounts that were intended for your vehicle and those are the OEM dealer supplied mounts. If after installing the correct parts, you still have a vibration issue, at least at that point you can continue on with further diagnostics knowing that the mounts are NOT an issue. Motor mounts are not what they were years ago. Modern mounts have internal hydraulics and valving. There are many, many parts on a car which should not be repaired with aftermarket (or worse, rebuilt) parts if you desire to keep headaches to a minimum.

I put my 05 nissan altima in neutral to push it because it won’t crank now it will not go past neutral to go in park.
ANSWER : Have you tried depressing the brake pedal while the key is set to run to see if the lock will release? You may have a park/neutral locking solenoid starting to fail. The cranking and no start problem could be something like a failed camshaft or crankshaft position sensor. Consider hiring an experienced technician like one from YourMechanic who can come out and take a closer look at the stuck shifter and no start concerns in order to offer a more personal diagnosis.

My car always stuck in neutral I’m trying to put into drive still showing neutral, putting in R still showing N 2015 Fiat 500
ANSWER : Hi there – your Fiat "automatic" transmission is actually a 6-speed, dual-clutch manual transmission, with some rather sophisticated electronics and actuators attached to it. These boxes are notoriously complicated, with incredible complexity in the transmission controllers themselves. Your controller is having a problem deciding what gear it’s really in, and not selecting anything (as you have experienced). There are actually 2 Fiat Recalls (#16V302000 and 15V291000) on the gearbox. I would take your car back to your servicing dealer, and have them resolve this. They have the tooling and software update capabilities to resolve these kinds of issues. Good luck!

My car idles high when coasting in neutral the revs stays at 1100 till i come to a complete stop
ANSWER : This may be a sign of a vacuum leak. High idle speeds or in some cases rough idle, stalling and hissing sounds are common signs of a vacuum leak. When a vacuum leak is present in an engine, this causes an excessive imbalance in the air/fuel ratio which creates a loss of power and causes the motor to run at a much higher RPM as a result of the increased oxygen present in the fuel charge being injected into the motor. This may also be caused by an idle control valve that may be sticking or failed due to old age or deterioration. I would recommend having an expert from YourMechanic come to your location to diagnose your vacuum leak as these can be very difficult and time consuming to trace.

Is my mechanic responsible for engine damage?
ANSWER : Hi there. I have a few questions for us to ponder as we probe this concern. Did the vehicle overheat since the repair? Is the vehicle currently overheating? Is the check engine light on? If so, what are the stored codes? Was the water pump inspected/replaced? Thermostat? Are there any noises emanating from the engine? What is the current oil level and condition? Transmission fluid level and condition? As you can see, there are some unknown variables that we need to consider prior to placing blame on anyone. What I can help you with is that the idle air control valve has to have engine coolant running through it to properly set the idle and allow the vehicle to start and continue to idle. Also, a blown cylinder head gasket can create difficulty in starting and will be followed by possible overheating or drivability concerns. I suggest having a qualified technician perform an inspection to avoid a "he said, she said" and replacing unnecessary parts. Your Mechanic has several available technicians that can assist you with a car is hard to start inspection.

My engine started misfiring on my way home from work today. should I have it towed to my mechanic or is it safe to drive to have it fixed.
ANSWER : Hi there. It is not good to drive a vehicle with an engine that is misfiring and running rough as it can damage the engine. When the engine light was flashing, that meant that something went wrong at that moment and with the gauges fluctuating, there could be a loss of electrical connection or a serious engine problem. I recommend having your vehicle towed to prevent any damages to the engine. If you need further assistance with engine misfiring, then seek out a professional, such as one from Your Mechanic, to help you.

My car will not shift out of drive and into park – 1999 Hyundai Sonata
ANSWER : Hi. This sounds like the ignition switch has a problem and is not allowing the car to go into park. If the ignition switch is not sending the signal to the neutral safety switch that the key is in the run position, it will not allow the shifter to move. It is also possible that the shift linkage is damaged and is causing the problem you have as well.

I suggest you have a certified technician, such as one from YourMechanic, come to your location to determine why the car is not shifting properly and suggest the necessary repairs