Fuel Efficiency in an Autoamtic vs Manual


#1

I recently purchased my first automatic after driving stick for 20 some years. I always shifted into neutral when going down hills and drifting to a stop to reduce drag and increase efficiency. Is this safe to do in an automatic or am doing damage to the transmission. In a stick I would just match the rpms so it slid back into gear when the drift ended.


#2

Put it in “D”, leave it there, worry about something real, and don’t look back…You sound like the perfect customer for a hybrid vehicle…Dream about that…


#3

Experiment with your vehicle and you may find you gain nothing. Depends on the transmission and electronics.

For example, on both of my newer trucks, 06 Escape hybrid & 08 Expedition, the electronics keep the engine rpm very near hiway speed-----it DOES NOT drop to idle rpm therefore I gain nothing by shifting to neutral at any speed…so I don’t.


#4

@Caddyman – they don’t make a jeep hybrid but I hear they might. Not sure I’d buy one since the money you save in gas would get eaten up by replacing batteries, not to mention the initial outlay.

@Ken – True enough but I don’t want to experiment to find I am saving 10% on gas but kill the transmission.


#5

Doing it in a modern automatic is harmless and completely without value. The computer protects the tranny, with the exception of the bit of extra wear on the shifter linkage.

In a manual tranny all you were really accomplishing was reduced wear on the brakes. But I’ll add that it sounds like you understand the principle of rev matching when shifting and that’s a good thing. It saved you a lot of wear on the clutch assembly and drivetrain.


#6

In the manual I was getting 10%+ better gas mileage. By shifting to neutral I was reducing the drag that the transmission puts on the car when not supplying power allowing the drift time at reduced RPMs to be increased.


#7

Ah, but now you have a Jeep with an automatic. :slight_smile:

If you have the AWD version, let the Jeep do that portion of the thinking for you. Just keep the tires all rotated and in good condition, and keep up with the services. It’ll do just fine.


#8

This is asked over and over and over here. Please search for the previous discussions, which apply to you too.

In short, it uses more gas, it’s less safe, and it’s often illegal.


#9

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What he said.


#10

Yup!
It uses more gas, is not a safe practice, and is illegal in many/most states.


#11

Even with a manual, using neutral would be extremely difficult to measure a claimed increase of 10% in gas mileage. There are just a few instances where shifting into neutral might be advisable, non of which has anything to do with economy. To anyone who does this, please find something in writing that recommends this practice by any professional in the automotive world.


#12

It varies somewhat from car to car. For example many new cars will shut off the fuel when you car is moving faster in gear than the programed idle speed. That means you are getting infinite MPG.

Frankly there is not a lot to be gained once you are driving conservatively. High speeds tail gating etc. will cause additional fuel usage.