Coasting in Neutral

goser · #1 10-26-2006, 10:57 PM

I tend to like to coast down big hills and take slow stops on my long trip to work and I realized the other day that it was weird that my RPM stayed at the same level while doing this as it would if I were giving 'er gas. So I started shifting (my automatic 98 Jimmy) into neutral as I stop and the RPM's drop down significantly. I figure if I did this religiously I could make a small dent in my mileage, but I'm wondering if this is normal, or if all the shifting back and forth could cause problems. Also, when I decelerate in neutral the fuel guage plummets dramatically; it goes from half a tank to turning on the low fuel light--can anyone explain this?

muddog321 · #2 10-27-2006, 05:11 AM

Yep, you are a dreamer and slower speeds (ie lower rpms) and slower starts are biggest savers and AC off adds another 2mph usually. Short term the trans will be fine as for constantly doing this I would have to guess the trans internal pressures are dropping when you go to N then have to boost quickly and this was not a design consideration for daily multiple occurrance. I would keep the tires inflated to 35 psi and if a real issue get a small car! As for the gage, the fuel pump is nera the rear and a long tank and the level senders are a known problem in all - GM has a newer robust design (and part of the pump) so do it youself is apprx $400.

goser · #3 10-27-2006, 02:05 PM

Yeah, I'm all for saving money and the environment, but I still can't give up my truck, so I'm just trying to get as much out of it as possible. I was half looking at the hybrid Escapes though...

The weird thing about the fuel guage is if I make a sudden stop in drive the needle dips two or three ticks, maybe a quarter of a tank tops, but when I make the same stop in neutral it drops from half a tank to dead empty. The first time it happened last night it freaked me right out--I thought for sure I'd look back and see my fuel tank rolling down the road behind me!

ZL1power69 · #4 10-28-2006, 12:00 AM

shifting from drive to neutral to drive everytime you stop is not gonna help with fuel economy and will probably cause tranny issues down the road.

peterjon1 · #5 10-30-2006, 06:03 PM

Take those $.02 gas savings and put them in a high yield savings account to pay for the new tranny. And if you're coasting down long hills in neutral. are you using the brakes more to control your speed, thus increasing brake wear?
I know that some trannys don't pump fluid (thus Lubrication) in neutral. Not sure if ours falls into that category. Something to think about, are the teeny savings now coing to cost a whole lot later?

BlazerLT · #6 11-02-2006, 01:12 AM

Quote:

Originally Posted by goser

Yeah, I'm all for saving money and the environment, but I still can't give up my truck, so I'm just trying to get as much out of it as possible. I was half looking at the hybrid Escapes though...

The weird thing about the fuel guage is if I make a sudden stop in drive the needle dips two or three ticks, maybe a quarter of a tank tops, but when I make the same stop in neutral it drops from half a tank to dead empty. The first time it happened last night it freaked me right out--I thought for sure I'd look back and see my fuel tank rolling down the road behind me!

Yes, the fuel rushing to the front of the tank will have the sending unit nearer to the rear to have a lower reading.

Cruize · #7 11-02-2006, 12:21 PM

Quote:

Originally Posted by goser

I was half looking at the hybrid Escapes though...

If you get another daily driver, get a manual transmission so you throw it into neutral easier. Of course, you'll end up with a lot more wear and tear on your entire clutch system.

frehol · #8 11-02-2006, 03:22 PM

I'm not sure how it works with a automatic trans. but with a manual going downhill using the engine as a break: No gas is used 'cos the engin is turning anyway (over idle RPM). In neutral it needs some gas to idle, thus consumes more...
This apply to most injection engins with electronic control so I suppose it apply to ours too.

Any comments? Am I totally wrong?
/Freddy

blazes9395 · #9 11-02-2006, 06:10 PM

While a manul transmission for this is the best option, an automatic tranny is also used for engine braking when its in gear, both when the TCC cluch is connected or even when it is disconnected (you still have fluid coupling within the convertor). You won't save gas at all, if anything you might use a little.

The problems with this shifting into neutral idea are that there are risks.

1) Lets say if you were stopping, threw it into neutral, and all of a sudden, you nedded to avoid a possible accident, by the time you threw it back into drive, (assuming you didn't react adversly and by mistake threw it into reverse), by the time you put it back into gear, and by the time the transmission actually engaged after you put it into gear, you could be to late and in an accident.

2) As stated above, its very easy to go a step further and knock it into reverse, there goes a good tranmission.

3) If you did this for stop and go, over and over, or if you used this method of braking down hills for a long time, you could easily overheat your brakes(because of a lack of engine braking), wipe your brakes out and bingo, no brakes. Thats the reason gearing down long hills with a load is safer and keeps you more in control by controlling speed thereby not using your brakes constantly.

4)Basicly just wearing out things like brake parts and stuff much faster. the possibility of damaging your transmission, etc., etc.

All in all, this will not save you any gas, and might make driving a little more dangerous.

blazee · #10 11-03-2006, 05:48 AM

^^ I agree.

Not to mention that coasting in neutral is illegal in most states....

316.2024 Coasting prohibited.--The driver of any motor vehicle, when traveling upon a downgrade, shall not coast with the gears or transmission of such vehicle in neutral or the clutch disengaged. A violation of this section is a noncriminal traffic infraction, punishable as a moving violation as provided in chapter 318.

BlazerLT · #11 11-03-2006, 07:52 PM

Quote:

Originally Posted by blazee

^^ I agree.

Not to mention that coasting in neutral is illegal in most states....

316.2024 Coasting prohibited.--The driver of any motor vehicle, when traveling upon a downgrade, shall not coast with the gears or transmission of such vehicle in neutral or the clutch disengaged. A violation of this section is a noncriminal traffic infraction, punishable as a moving violation as provided in chapter 318.

I wonder why and if they could prove it during a collision.

blazes9395 · #12 11-03-2006, 09:32 PM

Quote:

Originally Posted by BlazerLT

I wonder why and if they could prove it during a collision.

Actually they can obtain the information if needed, if that was what was in question in an accident investigation. While I dont agree with it in general, as it, in my opinion, infringes on privacy laws. The newer ('98 and on for these trucks) can now access vehicle drivng parameters through a vehicle module, that records speed, gear position, whether the person was applying brakes etc etc. The information can be obtained.

ZL1power69 · #13 11-03-2006, 09:37 PM

i believe from 97 on up vehicles (at least gm) have "black boxes" that record vehicle data that can be retrieved to find the cause of a crash, just like an air craft.

BlazerLT · #14 11-03-2006, 10:09 PM

Thanks guys, just a curiosity.

That is crazy how they can do that.

Guess it keeps us honest.

blazes9395 · #15 11-03-2006, 10:11 PM

Quote:

Originally Posted by ZL1power69

i believe from 97 on up vehicles (at least gm) have "black boxes" that record vehicle data that can be retrieved to find the cause of a crash, just like an air craft.

GM started using systems like this back in '95 and even ( I have to verify) I think in the '94 Oldsmobile Cutlass, so even back to starting in '94. I know for sure in '95 in some cars such as the monte carlo, the chev lumina, for example.

This system is a part of the air bag system, especailly vehicles with dual air bags. So basically if you had driver and passenger air bags, you could very well have this black box module, so to speak.

Even further, new GM vehicles that have OnStar, can gain this information without even touching your car, so to speak. A little food for thought, talk about big brother.

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