Is it better to idle in NEUTRAL or PARK?

[mareakin]

Just curious, which is better?

I am thinking that maybe idling in Neutral is better, and I speculate, I guess, the reason is that in Neutral the engine is "disconnected" from the transmission in some sense and since you're not moving anyway, more engine power can be used to power the accessories such as the air conditioning compressor or the alternator.

I think it's obvious that I don't know what I'm talking about.

Just a guess.

Please chime in.

 

[eljefino]

Park = neutral as far as the engine side of things look. Just a pawl holding it from rolling.

Though apparantly the old dodge 727 transmissions were hydraulically different, and filled TCs faster in Neutral.

 

[XS650]

Originally Posted By: mareakin
Just curious, which is better?

I am thinking that maybe idling in Neutral is better, and I speculate, I guess, the reason is that in Neutral the engine is "disconnected" from the transmission in some sense and since you're not moving anyway, more engine power can be used to power the accessories such as the air conditioning compressor or the alternator.

I think it's obvious that I don't know what I'm talking about.

Just a guess.

Please chime in.


Back in the olden daze there were some automatic transmissions that didn't run oil through the oil cooler in park. For those neutral would be better.

I would guess that most modern ATs have that problem, but it's worth finding out if yours does.

 

[ARCOgraphite]

The converter helps damp the engine vibrations and harmonics so in drive is better for the motor ALA the idle isnt too high (above 750)

 

[mechanicx]

As far as your question of more engine power to power the accessories when in N or P vs Drive, that use to be sort of true in the days of carburetors (and some earlier FI engines without idle speed controllers like some Japanese). Nowadays engines either have a idle speed controller or throttle by wire and the idle speed is kept constant regardless of load.

 

[gathermewool]

Originally Posted By: mechanicx
As far as your question of more engine power to power the accessories when in N or P vs Drive, that use to be sort of true in the days of carburetors (and some earlier FI engines without idle speed controllers like some Japanese). Nowadays engines either have a idle speed controller or throttle by wire and the idle speed is kept constant regardless of load.


This.

Maybe the OP meant N vs D? If that's the case, I'd suggest keeping it in D to minimize band wear. My assumption is that, with proper fluid maintenance, the extra heat generated, even in stop and go traffic will be negligible - the bulk temp, I would think, will remain just above coolant temperature at worst. The only negative is obvious; load. With the car in D, the engine has to work harder to maintain idle RPM. Just as when you turn on an accessory, putting the car in drive will increase gallons burned per hour. IIRC, in my old Suby I would see fuel consumption increase from .29 gph to .36 gph fully warmed up from N to D, respectively.

 

[mahansm]

We need to define "better" in this context. It could mean lower fuel consumption (with air conditioning on, shifting from D to N lowers consumption from .65 GPH to .5 GPH in my Odyssey), less heating in the transmission (P/N, same for both on modern transmissions), less risk of transmission damage if the car is bumped (N), less chance of the car rolling away (P), quicker engine warmup (D, more load/fuel burn), or other.

As stated above, with idle speed control there is sufficient engine RPM to run accessories with any transmission setting; engine speed should stay the same in any gear. Engine speed may be increased when the air conditioning compressor runs.

Steve

 

[garlicbreadman]

i always put in N since N is right above D. less throw

 

[crinkles]

Originally Posted By: ARCOgraphite
The converter helps damp the engine vibrations and harmonics so in drive is better for the motor ALA the idle isnt too high (above 750)


Really?? my engine is noticeably rougher in D with my foot on the brake than in neutral...

 

[SteveSRT8]

In any modern car it is a waste of time to put it in neutral unless you're going to be sitting a LONG time.

The car knows what to do. My GM products will even adjust the idle up to raise the alternator output on days when the AC is maxed out.

 

[ARCOgraphite]

Originally Posted By: crinkles
Originally Posted By: ARCOgraphite
The converter helps damp the engine vibrations and harmonics so in drive is better for the motor ALA the idle isnt too high (above 750)


Really?? my engine is noticeably rougher in D with my foot on the brake than in neutral...
Unwanted Harmonics and chain or belt slap etc. Not roll or misfire. On my MT my car is usually in neutral when at a stop to prevent throwout wear.

 

[mechanicx]

Originally Posted By: crinkles
Originally Posted By: ARCOgraphite
The converter helps damp the engine vibrations and harmonics so in drive is better for the motor ALA the idle isnt too high (above 750)


Really?? my engine is noticeably rougher in D with my foot on the brake than in neutral...


I can't say I agree ARCO. The converter is always connected to the engine. Putting the AT in gear only serves to increase the load, via the pump through the Drive circuit, and nothing else.

 

[mechtech2]

New computers will raise the idle [so it is the same as neutral] when in gear and stopped. But if the car can roll 5 MPH forward in gear at idle, this is power , heat, and fuel wasted.
I take it out of gear if I am stopped for 10-15 seconds or more.
I would never put it in park unless I am safely parked, first.