We are the last of three houses on a 0.5 mile private gravel lane. The lane doesn’t get plowed or salted, but we can usually get in and out OK. (Western PA)
My gf drives a Subaru (Impreza?) with automatic transmission. I was her passenger the other day. The first 25 yards or so of the lane is downhill with a bend. I usually put my vehicle in 4WD and drive slowly.
I noticed my gf shift. I assumed she was using her 1st gear, but then realized she was in neutral. She said that was better in her car. I was surprised.
Depends. What your gf is doing is usually recommended for standard transmission cars. For an automatic, it might put a little more wear and tear on the tranny, but you might use less gas. What you are doing is safer, but I don’t believe it to be necessary and probably uses more gas and puts more wear and tear on the tranny.
On any kind of loose surface, especially in an AWD vehicle, you are far safer leaving the transmission in gear and letting the AWD (probably coupled with stability control) do its job. Wear and tear and gas are probably incomputable minimums lost in the statistical noise.
NitroPress is right. I’d have to assume your gf is having a hard time controlling speed in drive and prefers to just brake while in neutral. But then she has no control if she loses traction.
Using engine braking does add some wear and tear. However, the vast majority of that wear is to surfaces that are rarely loaded in otherwise normal driving…the back side of gear teeth, splines, U-joints, etc.
In manual transmission cars, coasting in neutral may pose a small risk of the engine stalling, causing loss of power steering and power brakes. This is a risk in automatic transmission cars even in gear. Modern Fuel injected cars seldom stall, but it was not uncommon with carburetors.
When going down a slippery hill it is better to put in neutral and use the brakes only.
The reason is that sometimes the engine brakes too much and might lock the wheels.
Some 4x4s have automatic hill descend. You put the car in neutral, select a descend speed and let it roll downhills. The computer brakes each wheel independently so not only the car maintains a constant speed, but also there’s no risk of losing control.
No, you will use no “gas” if you have zero throttle on a modern fuel injected car that is in gear but not if it is idling, it will have to be above a certain RPM - let’s say 2000 to be on the safe side - and effectively the engine’s compression is used for braking.
That isn’t going to be the case with how the girlfriend is driving.
By the way as has been alluded to by others here when you do extreme off roading you will find that using the brakes at all can be the first step to using control. The procedure for descending a super steep hill is to stop at the top, select low range if it’s not already selected and vehicle is equipped with it, select first, and let the clutch out and have it descend on that. Toucheing either the clutch, the brake, or the accellerator can lead to tragedy.
That is not a situation analagous to the OP though. To be honest doing almost anything will be good enough and not worth sacrificing sex for to argue about.
Other than in hybrids and certain very high efficiency cars that shut the gas engine off while sitting at a standstill, I don’t know of any gas engine that uses zero fuel while nominally running. Do you have a cite for something different?
Diesels are very nearly such a case; they throttle the engine by the amount of fuel injected and at idle run on a bare mist of fuel - but not nothing.
As I made completely clear, the cars are not shutting the fuel off when they are idling. They are shutting the fuel off at zero throttle when the engine is at sufficient speed, this is a different thing entirely. You need the car to be in gear and moving for the fuel to be cut off for more than a fraction of a second, but this is hardly an uncommon situation!
There are various hills where I will descend for a couple of minutes using no fuel at all and I don’t live anywhere very hilly (by international standards I am hilly indeed by populated british standards)
Bag of cite: http://www.popularmechanics.com/cars/alternative-fuel/news/coasting-in-neutral-fuel-economy. Hope this ends the confusion - you really do get infinite mpg coasting in gear on zero throttle in a modern fuel-injected car. And staying in gear when coasting downhill is more stable than popping it in neutral as you’re unlikely to stall* (as mentioned by Kevbo), the brake servo will stay nicely pressurised as the faster-than-idling engine speed will be pumping clean air out of the exhaust, and the transmission will add considerable damping to the rotary motion of the driven wheels so they’re less likely to snatch and lock under braking.
*My favouritest car what I’ve owned was a Citroen XM - if the engine stalled on that you had a few seconds before the hydraulic system depressurised and you lost power steering, brake servo and suspension. Concentrated the mind wonderfully.
I drove a borrowed Xantia once that obviously had something wrong with that bizarre system - when you braked the brakes bited to the “setting” you had chosen with the pedal, then released a bit, then went back to the asked for setting over the course of a couple of seconds (if you understand what I mean) - just on the offchance you’re a citroen nerd any idea what was going on there?
Mind you the ride in those things was magnifique. And also I think that the brakes were the last to go in a failure, you would lose steering then suspension first, not quite as dangerous as you make out but I may be wrong?
Sucker for punishment, me. XMs were like huge Xantias, and I believe the system architecture was very similar. As the hydraulic system went everywhere it could give rise to some very holistic faults: there’s a chance that your weird brake fault was quite unique to that car. For that reason, most garages won’t touch Citroen hydraulics.
I only drove a few hundred miles in it, and I know it ended up in the scrapheap not so long after I handed it back.
It has to be said that while it was very slow (i have a feeling it was a 1.9td… with broken turbo… but I may be forgetting) in comparison to what I was used to the handling was still genuinely amazing, and I loved playing with the ride height (often inappropriately :D)
That fault could have led to driver induced oscillation, to coin a new phrase - once you were used to it you worked around it but very strange.