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Driving in Neutral on a manual transmission Nissan Sentra

I recently bought a used 2001 Nissan Sentra for my sons use in his senior year in high school. He has been driving a month and he has decided that the best way to save on gas is to use neutral on the hilly roads in our CT town.



Please help me explain why this is a really bad habit to get into.

Thanks

Cathy

I don’t consider it a bad habit on a manual transmission but that all depends on the driver and how they handle things. Gas savings? Negligible.
If the car had an automatic I would not advise shifting the transmission in and out of neutral constantly.

Just my humble opinion anyway.

Your son has no idea what he’s talking about, and his “shift into neutral” theory may lead to his demise.

Yes, it could kill him. Coasting downhill is very dangerous. He should not be doing it.

Shifting into neutral going downhill is totally crazy. It reduces the driver’s control of the vehicle, while it offers NO improvement in fuel economy. Your son doesn’t understand how modern fuel infection works.

In neutral or in drive, you son’s Sentra will consume the same amount of fuel. The engine computer will maintain idle speed regardless of the speed of the car down a hill. Idle speed requires very little gasoline.

Take away his keys until he understands this.

Please.

"In neutral or in drive, you son’s Sentra will consume the same amount of fuel. "
Not true.
In gear going down a hill, the engine will consume no fuel at all, the engine computer turns the injectors off.
In neutral, the engine will consume enough fuel to maintain idle.

Driving in neutral is costing him fuel/money, not saving it!

AND hard on bakes!!

In a respectful tone, I’d like to ask how coasting in neutral reduces driver control of the vehicle and an explanation of how in the world an engine will run if the injectors are turned off.

Engine braking will help maintain control going down hill, instead of over using brakes, potentially having fade set in. And the engine drag keeps the engine turning, no gas needed.

Sounds like he is saying one must use a lot more brakes, if I understand him.

The real problem is when a driver decides to let it fly, to coast up the other side. The high velocity where it may not be safe is decidedly dangerous.

That alas is what most neutral coasters end up doing, and so I am told in many areas it is a guaranteed ticket to coast in neutral.

Here in the mountains, a couple hundred yards from my driveway is a steep hill down, with very rough rocks. I find the normal idle speed, especially when cold, tends to be enough faster than the car’s speed that I find myself using a lot more brakes. So, I tend to shove it into neutral so I can go slower without excess brake wear. That is an unusual circumstances, due to the low speed needed on those rocks. These mountain people are tough and often they walk faster downhill than my car is able to go on those rocks.

When you air up your tires, you turn on an electric motor and that motor drives a pump.

Think of an engine as an air pump that burns fuel. It needs to pump in air before it can burn fuel. The energy from the fuel burn pumps air into other cylinders as well as provide propulsion. When you’re rolling downhill in gear, tires turn the transmission and it turns the engine. The computer usually cuts out fuel if no throttle is applied and the engine behaves as a pump without burning fuel.

This pumping action is engine braking and, in general, it should be your primary way to control your downhill speed. No engineer can design a brake system that will hold your speed for EVERY hill. If you overuse your brakes, they can possibly fail temporarily, right when you need them the most.

Once a while, I’d smell brakes on a downhill drive. 30 seconds later, I’d see a semi with thick, gray smoke coming from its brakes. That’s what happens when they miss a downshift and ride the brakes downhill in neutral. I hope this is graphic enough for the OP.

OK4450, the engine doesn’t “run”, it is turned by the transmission. Why is this hard to understand. Remember how cars used to be push-started? It’s the same thing. If you don’t believe me, Google the patents on-line. They are available to look at.

I ride a 2001 Kawasaki ZRX1200R motorcycle and when gas got really expensive, I started coasting with the clutch disengaged down any hill that was steep enough to maintain speed with gravity alone. If the hill was not quite steep enough, I would coast and occasionally accelerate back up to speed with a short pulse of power. Also, I coasted to all red lights with the clutch disengaged.

This increased my gas mileage from 44-48 to 50-53 mpg. My best tank ever was 56 mpg done by killing the engine during coast and waiting at red lights with the engine off but I don’t do that anymore because I’m afraid it’s too hard on the starter.

With my 5 speed Yaris, I freewheel unless I need engine braking to keep the speed in check or I am approaching a red light so hot that I’m going to have to brake anyway. My best ever gas mileage in that car was 46 mpg and I routinely get 43-45 mpg.

What kind of gas mileage is your teenage son getting? Personally, I would feel a lot better about my kids trying to set gas mileage records than constantly trying to show the world that that they can drive 100 mph.

Isn’t your Kawi carbed, no FI? In that case it’ll save a little gas. Does not apply to FI cars.

Driving the car while in neutral (out of gear) is considered dangerous. It is illegal in Virginia and in many other states; it can result in a traffic violation called “Coasting”

I put all the technical issues aside,fuel,brake fade,steering and just say the concentration factor of wondering if I am in or out of gear and the potential need to be in gear quickly to be the main issue.

Teenage drivers with thier own cars crash more,all over the net and newspapers lately.