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o/t Fuel Saving Idea ????

T

Tom B...IN

Member
Driving home tonight I had a thought on how to save fuel and thought I would present it to the board (ya'll).

When driving a vehicle with an automatic transmission would it hurt to put it in neutral when you know youre coming to a stop? For Example My drive way is about 3/4 the way down a long hill when coming from one direction. Once I know I have enough momentum to get into the driveway (ie top of the hill) could I put it in neutral and cost to a stop in my driveway (using the brakes too) and then put it back in drive?


It seems to me that as long as you come to a complete stop before going back into drive it would be ok, and save fuel. or am I wrong?


Thanks Tom
 
I think i heard somewhere it would. Funny thing, is if yall put this kind of thinking into inventing something or other and getting it to sell, you could buy more then gas.
 
Why would you haveto come to a stop to put it back into drive, if you are coasting foreward it will not hurt to shift back in. Not into reverse though.
 
Not a bit. I do that a lot with my older cars with auto trans in them. in fact i don't even come to a stop before shifting back into gear - it's all about fluid motion anyway in most modern trannies so it won't hurt anything.

I find that it improves economy because it is wasted energy and fuel pushing against the brakes. Additionally, in cars that like to stall at stop signs like mine, if you figure out the gas pedal you can avoid the engine stalling.

I believe this is a concept in the newer cars from some manufacturer, nissan maybe. They rigged it to the brake pedal so if you step on the brakes it shifts the tranny back to neutral.
 
Forget it My 69 Saab Sonett has free wheeling in it I got the same mileage with it engaged or disengaged. 30MPG
Walt
 
Also for better fuel economy in an auto trans vehicle I would recommend learning to drive as though you have no brakes. I don't mean downshifting like an auto transmission through L2 and L1, but rather driving easy on the gas and coasting 1/3 of a mile to that stop sign while the engine quietly idles along. Of course this works better in diesel trucks, but it also helps in gas cars.
 
Tom I'm not a mechanic, but I kind of think that an automatic transmission has clutches in it so that when you let off of the pedal also lets off of the power and really doesn't do anymore that if you were idling in nuetral anyway. I could be wrong though, and understanding automatic transmissions isn't my strong suit. Kind of seems like a lot of work though, and I'd guess that engaging it (in drive, in nuetral, in drive, etc) probably oughta be some wear and tear too. Again, I could be wrong. As far as manual transmissions go, probably would help some to slide it out of gear when... I only use my clutches for initial take offs in forward or reverse anyway. After that I just left back on the fuel and time easing it into the next gear. Saves on the clutch, and if do it right and easy enough, no banging gears as the teeth mesh.

Good luck.

Mark
 
the only reason i said come to a complete stop was i didnt know if it would create too much of a "jerk" in the driveline and eventually do damage
 
I read recently where someone thought this was a good idea and accidentally hit reverse, cost them about $1500 for a new transmission. As long as your foot is off the gas pedal, I don't think your burning much gas, I doubt if you ever save enough gas to pay for all your brake rebuilds! Just coast when it's feasible, saves fuel and brakes!
 
Thats just about the same idea as putting my 5-spd. F-150 in neutral as I coast up to stop signs, insted of leaving it in gear. Won't pass a CDL test that way, but it may save me a little when I'm just pokin' around :)
 

Nope, not gonna save you a dime... In fact, in the long run, you are going to spend more money rebuilding your brakes. I know that on my '99 Ford Taurus, when I let off the gas, the engine actually is utilized to provide a very small amount of "engine braking". Putting an automatic vehicle in neutral while coasting is just not a good idea. Just drive it easy and don't make a hassle out of driving by having to do stuff like putting a trans. in neutral etc. Maintenance and easy driving habits are the keys to efficient driving...
 
wont save a thing, other than using moderate driving tactics, [ start smoothly no jack rabbit starts ect and making 1 trip work for multiple tasks] there is only 1 tried and true method for saving gas, dont burn any, use other methods to get around , ie public transportation in urban areas human or electric powered vehicles, and the most interesting way is the original suv, a horse, all these mini ranchers and horsey farms have them i wonder if they ever thought to slap some leather on them and use them? for trips under 10 miles all around
 
Yes and a free wheeling vehicle is harder to handle and a more dangerous situation..exactly why it is illegal in many states and provinces
 
I coast with a stick shift (in my small truck). Wouldn't be any real reason to in an automatic.
 
May save gas BUT is your in a wreck and they can prove you where not in gear you are at fault. Its not legal to drive with a car or truck that is not in gear because your not in 100% control of that car or truck. That's even in the drivers manual or at least it is in all the states I have had a license in
 
The brake pedel is harder on mpg than the gas pedel. It seems rural road stop signs are always at the bottom between hills. Braking losses all your momentum then acceleration up the following hill. A little thought when placing stop signs could double mileage.
 
With a carbureted engine, you might save gas because the engine can suck gas through the idle jets when the manifold vacuum is high. But a modern engine with fuel injection just about completely shuts off fuel to the engine when coasting, so it really doesn't make much difference whether you're in gear (at partial throttle) or out of gear (at idle).

The real reason not to coast is safety, as others have said. There is a reason it's illegal.
 
Yes, wouldn't it be much better if all stop signs were at the tops of hills? That is where all the crossroads are. Right?? :)
 
Where did you get that Crap from I have over 350K on my Saab with free wheeling its legal to drive in all 50 states.
Walt
 
Hi tom,

If your engine is a DBW(drive by wire) fuel system,then you will use more fuel while coasting out of gear. Doesn't matter what tranny you have.

A DBW system shuts off the fuel when the fuel pedal is at idle position until the rpm drops too 100rpm above set idle rpm, then the engine will idle. It works this way on both gassers and diesels.

I use this too increase my fuel mileage on my 02 F350 PSD. I either apply fuel or don't apply fuel. There is no inbetween throttle position use. If I want to slow down, I remove my foot off the fuel pedal.

T_Bone
 
My '48 Hudson free-wheels in overdrive- all of the independents, and Fords, used the same OD- all free wheeled. Kind of scares you the first time or two you use it.
 
Tbone is on the right track. It doesn't have to be throttle actuator equipped AKA drive by wire. All fuel injected vehicles have a fuel cutoff strategy in them to improve mpg. Shifting out of gear in an automatic would likely have the opposite effect since you could not go into fuel cutoff coasting + the PCM on many vehicles will hold the engine idle speed higher than normal to prevent the possibility of causing the drive wheels to skid on a slippery road when shifting back into drive.
 
If its working right, your OD doesn't freewheel 'til your speed drops to below 22 MPH or so. Albeit, there is not as much resistance going downhill in OD as in high gear but there is some. Shift into second while in OD and you will see what I mean.
 
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