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      04-10-2012, 09:57 PM   #1
BrazilianBimmer
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I'm dumbfounded!....Trying to save on gas.

Okay, I have an e90 streptronic 325i. I've read somewhere here that using the "manual" mode helps to use less gas. Here's my question, how do you change gears on this. First of all I don't know how to drive stick. So my question is not really how to change gears, but when to change them?
At what rmp/mph should one change from 2nd to 3rd...and so on?
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      04-10-2012, 10:33 PM   #2
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Keep it under 3000 rpm
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      04-10-2012, 10:36 PM   #3
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The Steptronic keeps it well under 3000 rpm unless you're hard on the throttle. Just leave it in D.
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      04-10-2012, 10:57 PM   #4
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Quote:
Originally Posted by BrazilianBimmer View Post
Okay, I have an e90 streptronic 325i. I've read somewhere here that using the "manual" mode helps to use less gas. Here's my question, how do you change gears on this. First of all I don't know how to drive stick. So my question is not really how to change gears, but when to change them?
At what rmp/mph should one change from 2nd to 3rd...and so on?
Unfortunately if you don't do it right, you will use more gas than d mode does... which, is actually pretty hard for you to beat manually if mpg is your only measure
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      04-10-2012, 11:05 PM   #5
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If you want to save gas you will have to shift at lower rpms than what the automatic mode will shift at.

Try 2100 for a smooth 2-3 shift
1600 for 3-4
1500 for 4-5
1450 for 5-6

You know you're shifting at too low rpms when the car blips the gas before shifting into the next gear. If you pay attention to the needle you will see what i mean. The needle should nicely drop to the next gear, it shouldn't bounce up first and you shouldn't feel the shifts; they should be smooth.

If you are coasting, you will be able to shift at lower rpms, like 1300 from 5th to 6th.
If you are accelerating, do not shift below 1500.

The best way to improve mpgs is to use your brakes less often. That means you should average your speed in traffic and you should time lights. As soon as you see a red light, just start coasting. And most importantly: Stay out of the fast lane.
You'll get the best mpg's at about 55mph. Sometimes there'll be big rigs cruising on the freeway at such a speed, and if you've got the time to spare, try following the big rig.
If you are between two big rigs, DO NOT tailgate the big rig in front of you. You will get pinched in between the two. I've seen pictures, it's tragic.

I recommend resetting the mpg-average every trip.
Do realize that you will have weak acceleration at low rpms. In the manual mode, the engine will not downshift when you step on the accelerator unless you reach the click at the end.

As for not knowing how to use manual mode: Practice will really help. Just try it, and know that you can't stall or over-rev the engine.
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Last edited by Verbatim; 04-10-2012 at 11:12 PM.
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      04-10-2012, 11:12 PM   #6
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Cool this makes a lot more sense. It this what is used with a stick shift? man I sure wish I had gotten a stick..would have forced me to learn
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      04-10-2012, 11:15 PM   #7
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Quote:
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Cool this makes a lot more sense. It this what is used with a stick shift? man I sure wish I had gotten a stick..would have forced me to learn
I think you would have to shift at higher rpms with a manual, i can't imagine going through gears one through six just to reach forty miles an hour. You could probably skip gears, like go from 4th to 6th and such. The automatic will not let you jump around, it will always engage the gears in order.

*Also whenever you coast, put it into the highest gear possible for the least amount of "engine-braking". Engine braking is when the vacuum inside the cylinders slows the car down because you are not giving it any throttle. When you coast, the engine pretty much shuts off and runs off of the drive-shaft.
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      04-10-2012, 11:21 PM   #8
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I've been personally averaging 26_ mpg with half city and half highway. I think i could pull 30+mpg with a 325i
Don't forget to enjoy that sweet inline six though. Open her up whenever you feel like it, but improve your efficiency during your regular mundane drives. No need to redline and then slam on the brakes between red lights. You'll be surprised at how many people accelerate until the last second when approaching a red-light. It's ridiculous to see when you're maintaining an average speed through the streets.

I'll leave my house and meet up with other cars going the same direction, and i'll always meet them at a red light eventually. You don't really lose much time by driving slower.

I've personally not noticed a difference with the AC on or off. If anything the instant-mpg (which you should have on the display when driving "efficiently") goes from 45 down to 42 on a flat road with ac on/off.
If you're giving up air conditioning to save a dollar or two on a fill up, you should be looking at other ways of saving money, like selling your bmw.
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      04-11-2012, 12:36 AM   #9
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Transmissions are usually programmed (in regular mode) to save as much gas as possible. Car manufacturers do everything possible to meet EPA standards.
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      04-11-2012, 12:48 AM   #10
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Quote:
Originally Posted by 328i M-Sport View Post
Transmissions are usually programmed (in regular mode) to save as much gas as possible. Car manufacturers do everything possible to meet EPA standards.

Correct, but in my case, I live in a hilly city and my commutes are short, so my historical average is 15 mpg. I often make 13-14 mpg between fills. Highway average is pretty good, around 27 mpg, on flat country.

I've been told my consumption is normal...
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      04-11-2012, 02:03 AM   #11
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leave it in drive and dont punch the gas to much thats the best way to save gas.
and if that fails take the bus
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      04-11-2012, 02:44 AM   #12
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You wanna save gas? Buy a Honda.
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      04-11-2012, 03:27 AM   #13
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A lot of you guys are giving him low shift points. No offense to op but don't forget he has a 325 which would bog down like crazy if shifted at 1800 rpms. Just let d mode tranny shift with a light foot
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      04-11-2012, 04:03 AM   #14
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I live in the UK and have driven manual cars for a long time. I am also on my 6th BMW.

Anyway, I have a very hilly commute to work with alot of speed bumps. I have recently bought an E91 330D Auto which replaced an E46 330D Manual.

My finding are that in hilly traffic, the manual was far better in terms of consumption. I would average around 27mpg in the manual as opposed to 21mpg in the Auto. The reason for this is that the car shifts gear too early and therefore requires a heavier foot to get the car accelerating after slowing down for a speed hump. Fuel would be saved if the roads were flat or you weren't about to slow down to a near halt a few seconds later but there is only so much an auto box can know about situations.

I have recently tested the manual mode out by resetting the MPG at the start of each commute. If change late, only when needed and make sure the car is in the right gear at the right time I can get 30mpg out of the journey. In fact that's what I achieved this morning. This is a substantial difference to keeping the box in standard auto.

The further your foot goes down on the pedal, the more gas you use. Just pay attention to the MPG needle and you'll see exactly how it correlates. Being in the right gear at the right time is crucial to getting a good consumption. For example, you're at 30mph cruising along, the auto box would have you in 4th by now (possibly 5th if slightly above 30mph) which is great for consumption if there is no need to change speed. However, the car in front turns off and you have to slow down and then speed up. You would be better off with your foot half way down in 2nd or 3rd to accelerate than having it all the way down in 4th to get the same acceleration.

In summary, keep your eye on the MPG needle, try and limit how far you ever push the gas pedal. If you feel the need to push the gas pedal further down to get speed you desire, change down and you'll see you don't need to be so heavy footed.

It's difficult to explain but you're trying to put the least load on the engine/gears. Changing too early and having to put your foot down further to get to a certain speed will not help mpg.
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      04-11-2012, 07:16 AM   #15
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In normal city driving with my manual I usually like to keep the engine at around peek torque. Therefore, I usually shift right around 3000rpm. I've found that this gets me about 23mpg city, which is ok.
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      04-11-2012, 10:42 AM   #16
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Thank you everyone for their input on this. It really helps me kinda understand how manual transmission works and how they always say that it is a better choice.
Having said that, I move on to say this directly to the douchie bags that always answer a legitimate question with "want to save on gas, buy a honda!"
This is part of knowing your car, how it works and how to get the most out of it. Just because we own BMWs and we are O' sooo luxury doesn't mean we shouldn't be interested on how it can perform at it's best.
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      04-11-2012, 10:56 AM   #17
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if you really want to save gas, just leave it in D and go easy with the pedal.

Manual car uses a little less gas is not because of when to shift, it is because of the tranny itself, manual tranny have different dynamic than auto when it comes to how to transfer power from the engine to the wheels, manual is just more efficient.

if you want to learn when to shift, that will be a different topic
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      04-11-2012, 11:01 AM   #18
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give gas down hills, coast up if possible (no traffic)
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      04-11-2012, 11:01 AM   #19
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Quote:
Originally Posted by J28 View Post
It's difficult to explain but you're trying to put the least load on the engine/gears. Changing too early and having to put your foot down further to get to a certain speed will not help mpg.
Agree with what you are saying in the post. (I also drive a 330d auto). The quoted sentence is generally true, but diesel and gas (petrol) engines have different characteristics and you can find that the BSFC map of the NA petrol engine suits slightly higher engine loadings to run the lowest consumption. Too light and you have more losses than running higher throttle settings.

Still best to experiment, and see the results.

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      04-11-2012, 11:03 AM   #20
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Quote:
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A lot of you guys are giving him low shift points. No offense to op but don't forget he has a 325 which would bog down like crazy if shifted at 1800 rpms. Just let d mode tranny shift with a light foot
Eggzactly. The 335i has loads of low rpm torque, but with my MT 128i and 328i, I've found the most economical lower gear upshift points to be around the torque peak of 2750 rpm.

But until the OP gets a feel for how his engine and transmission are interacting, light throttle in D is probably his best bet.

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      04-11-2012, 11:31 AM   #21
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I've found the most economical lower gear upshift points to be around the torque peak of 2750 rpm.

But until the OP gets a feel for how his engine and transmission are interacting, light throttle in D is probably his best bet.

Tom
A lot depends on the acceleration rate, as peak torque is measured at WOT. There wll be a much wider range of rpm where sufficient torque will be available for part throttle acceleration, say at 1/4 or 1/2 throttle acceleration. You want the slowest rpm where maximum mpg is obtained, also parasitic and frictional losses are at lowest values.

A part throttle torque graph/map would be very useful to see where change points are most suited.

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      04-11-2012, 12:18 PM   #22
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the key to good gas mileage isnt so much about gas pedal control.... its about braking

like others have mentioned you should coast as much as possible, if you see a redlight ahead you should coast or even slow down just enough that you wont have to stop completely at the red light

i avg 27mpg in my 335i (50% city) because im rarely hitting the brake pedal

not only will you get better gas mileage but you will save your self a lot of money for brake pad replacement
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