Is downshifting in an automatic bad for the transmission?

[Laconian]

Believe it or not, we actually like to talk about cars here.

Cars? In my SanDiegoSpin? It's more likely than you think.

[Rupert]

Seriously, it's a bloody car forum, and he's surprised that we talk about cars? The hell?

[cawimmer430]

I sometimes do this in the E320 and 118i when I see that far ahead there is a buildup of traffic. I remove my foot from the gas and let the car roll by itself and in the process it begins to loose speed. Then I might downshift on the transmission to a lower gear or two and then the vehicle really slows down. Usually I never do this, but sometimes, when I feel like it, I do. No big deal. The transmission can handle it.

[Submariner]

I sometimes do this in the E320 and 118i when I see that far ahead there is a buildup of traffic. I remove my foot from the gas and let the car roll by itself and in the process it begins to loose speed. Then I might downshift on the transmission to a lower gear or two and then the vehicle really slows down. Usually I never do this, but sometimes, when I feel like it, I do. No big deal. The transmission can handle it.

Once in a while it's fine.  All the time is just silly.

How are the E320 / 118 BTW?

More importantly, how is Claudia? 

[cawimmer430]

How are the E320 / 118 BTW?

Doing just fine. E320 has its summer tires back on. I'm taking the 118i on a roadtrip tomorrow to visit some exotic locations outside of Munich. 

More importantly, how is Claudia? 

In the US on business.


Oops, I gave away her current location. 

[Raza]

+1

It's pretty stupid.  Downshift if you want to engine brake, not when you come to a stop on a level road.  Automatic's do that for you...that's why they're called automatics.

Older automatics don't downshift all that often. 

I would downshift my Passat all the time (and you'd have to blip the throttle, definitely), and I tried it on my brother's E320, which had the 4-3-2-1 gate instead of a +/- like mine did, and it was not nearly as smooth.  It got to the point where it was such a hassle in his car that I didn't even bother.

[Submariner]

Doing just fine. E320 has its summer tires back on. I'm taking the 118i on a roadtrip tomorrow to visit some exotic locations outside of Munich. 


In the US on business.


Oops, I gave away her current location. 

I don't care about those cheap German pieces of shit, your sister is in the states?!?!?! 

I'll be your interwebz bff if you tell me where!

[cawimmer430]

I don't care about those cheap German pieces of shit, your sister is in the states?!?!?! 

I'll be your interwebz bff if you tell me where!

No idea where she is. Probably near Chicago like the last time. 

[sportyaccordy]

Cars? In my SanDiegoSpin? It's more likely than you think.

Upper middle class San Diego every problem is a crisis Spin.biz

[TBR]

+1

It's pretty stupid.  Downshift if you want to engine brake, not when you come to a stop on a level road.  Automatic's do that for you...that's why they're called automatics.

I almost always downshift when I am coming to a stop, does that make me stupid? It saves gas.

[Submariner]

I almost always downshift when I am coming to a stop, does that make me stupid? It saves gas.

Wouldn't staying in top gear reduce engine revs, thus save gas?

[Rupert]

I almost always downshift when I am coming to a stop, does that make me stupid? It saves gas.

No it doesn't...

[BENZ BOY15]

No it doesn't...

Yes it does, Psilos!

Actually, I don't see how that saves gas. You're probably right.

[Rupert]

It's fun and it sounds cool in a manual, if you match the revs, but it doesn't save gas. Save brakes, sure, make it so you slow down enough that you don't have to stop before the light turns green (which saves gas), OK, but if you are stopping, downshifting won't save you gas.

[Cookie Monster]

It's fun and it sounds cool in a manual, if you match the revs, but it doesn't save gas. Save brakes, sure, make it so you slow down enough that you don't have to stop before the light turns green (which saves gas), OK, but if you are stopping, downshifting won't save you gas.

Well, doesn't it engine brake and also turn off the fuel injectors so you're using no gas at all?

[hotrodalex]

Well, doesn't it engine brake and also turn off the fuel injectors so you're using no gas at all?

It engine brakes, but doesn't turn off the fuel injectors. Some modern cars turn off the injectors when you are in D and braking heavily.

[Cookie Monster]

It engine brakes, but doesn't turn off the fuel injectors. Some modern cars turn off the injectors when you are in D and braking heavily.

I thought whenever you coast in gear it turns off the injectors since the wheels are turning the drivetrain?

I must be mistaken...

[Laconian]

I thought whenever you coast in gear it turns off the injectors since the wheels are turning the drivetrain?

I must be mistaken...

It's dependent on the ECU's programming. I think some members have tried it for themselves and one (FordSVT?) got better fuel economy going down a hill while coasting than in gear.

[hotrodalex]

I would think with most cars, the injectors wouldn't turn off if you down shifted by yourself. I guess it would depend on the ECU, like Laconian mentioned.

[NomisR]

It really depends on the ECU, engine and transmission.  I would expect you're not going to get a lot of saving on downshifting on an automatic as the transmission is constantly slipping anyways. 

I don't usually downshift unless I'm going downhill when driving an automatic.  Street driving, if you spot up far enough, you can typically predict traffic to where you can just let go of gas and engine brake enough to slow down in an auto.  Unless you're driving a Toyota of course..

[TBR]

No it doesn't...

I have always heard that the injectors turn off when you're engine breaking. At the very least, it is probably using even less fuel than it would when idling.

[BimmerM3]

Oh, and congrats to Benz for his first automotive post and thread!

lol....

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[Rupert]

I have always heard that the injectors turn off when you're engine breaking. At the very least, it is probably using even less fuel than it would when idling.

Injectors? First, see above. Second, injectors? Third, why would an engine moving 3500 RPM be using less fuel than an engine moving 850 RPM? Even in this "injector" scenario, unless the injectors turn off, which some might, but not most, I would think that the injectors would be injecting the same amount of fuel as at idle (if not more).

Finally, injectors?

[Laconian]

Injectors? First, see above. Second, injectors? Third, why would an engine moving 3500 RPM be using less fuel than an engine moving 850 RPM? Even in this "injector" scenario, unless the injectors turn off, which some might, but not most, I would think that the injectors would be injecting the same amount of fuel as at idle (if not more).

Finally, injectors?

Read that as "petrol carburettor", then it'll make sense.

Why would an engine use less fuel coasting @ 3500 than idling at 850? Because no combustion is required to maintain that 3500 rpm, whereas the 850rpm idle is sustained by injecting and then exploding dinosaurs. Makes sense to me.

[BENZ BOY15]

Psilos, I don't appreciate your attitude.

[Laconian]

Psilos, I don't appreciate your attitude.

He feels left out when we talk about post-1975 technology.

[Rupert]

Read that as "petrol carburettor", then it'll make sense.

Why would an engine use less fuel coasting @ 3500 than idling at 850? Because no combustion is required to maintain that 3500 rpm, whereas the 850rpm idle is sustained by injecting and then exploding dinosaurs. Makes sense to me.

Oh, right. Now I get it.

Well if the fuel is being injected, then where is it going? If it's going somewhere, it's being used... I think that we can probably find cars that behave both ways, but as a general rule, as it was originally stated, I don't think any less fuel is used by leaving a car in gear or downshifting.

But, shit, I'm no expert (then, neither are most of the posters in this thread)...

[Rupert]

Psilos, I don't appreciate your attitude.

Blow me, kid.

Then take that out of context. 0_o

[Rupert]

He feels left out when we talk about post-1975 technology.

Five-speed transmissions? Since when?!

[Laconian]

Oh, right. Now I get it.

Well if the fuel is being injected, then where is it going? If it's going somewhere, it's being used... I think that we can probably find cars that behave both ways, but as a general rule, as it was originally stated, I don't think any less fuel is used by leaving a car in gear or downshifting.

But, shit, I'm no expert (then, neither are most of the posters in this thread)...

Why can't a fuel injector temporarily cease injecting?