automatic shifting question

[notenoughmoney]

I shift into neautral when I am coming to a stop my reason is to save gas and to possible keep wear and tear to a minimun by not having the gear engaged.... any opinions.

[BullShifter]

It wears more each time you engage into drive. The engine also doesn't like idling, but whatever floats your boat.

[crxlvr]

completly pointless, your motor is gonna idle at the same speed wether it be in N or D, plus your just chewing up the gears faster by always shifting it like that.

[rubix777]

you waste gas by shifting it to neutral. you know that the process of shifting, though it leads to keeping optimal rpms, if done more than frequently reduces your mileage. The engine uses the fuel more efficiently (more miles/gal) when it is in equilibrium. in other words, you get better mileage when you're cruising at a constant speed (freeway no traffic) verses fluctuating speeds(in traffic). same reason why city mileage is always lower than highway mileage.

best let the auto tranny do all the shifting for you. don't you think whoever invented the auto tranny thought about how things should change when a person is stopped at a light? they probably made it so that when it detects the brake being applied, it reduces the amount of gas for idling, to reduce how much you must apply the brake to stop the auto car from inching forward by itself. even if this doesn't happen, read previous paragraph.

[knorwj]

Originally Posted by rubix777

they probably made it so that when it detects the brake being applied, it reduces the amount of gas for idling, to reduce how much you must apply the brake to stop the auto car from inching forward by itself. even if this doesn't happen, read previous paragraph.

Actually doesn't it have to do with the fluid? like when you are sitting there the engine isn't rotating fast enough to propel the fluid, it just kind of swishes through it, and when you step on the gas it rotates faster and then is able to move the tranny fluid. hmm this probably isn't the best example but think of a boat propeler in water, if you spin it slowly the boat wont move but the propeller still spinning just not with enough speed to move the water, speed it up and the boat starts moving.

[Buzz1167]

The torque converter is probably what your talking about with all the fluid and "squishing". This device equalizes the tranny and the motor by using fairly viscous fluid spun by the engine side, and picked up by the blades on the tranny side (think of pointing a running fan into a non running fan, the non running fans blades begin to move becuase the running fan is forcing air through them, its basically the same idea except with fluid instead of air). While you idle, your engine is actually working to try to turn the tranny side, but since it isnt moving the engine side just keeps on trying (this is why - if you let off the brake, your car moves.) The only thing stopping it from moving are the brakes. So by disengaging the tranny it lets it freewheel at the same speed, whitch would translate into doing less work while idling, although re engaging the transmission all the time is probably where the extra "wear and tear" would come from. I dont think it would make any reproduceable increases in MPG unless you did alot of standing.
This is also the reason that most stick shifts get better gas milage, beucase the "squishing" is controlled completely by the driver, and usually doesn't happen for nearly as long as it does by the torque converter, not to mention that the manual is probably lighter.

HTH
Buzz1167
Jon N

[Sulsa]

I'll buy Buzz's explaination for a dollar. However, I bet it depends on how long you are sitting still each time, as to whether you save more money in gas, than you spend in repair bills on the transmission.