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      03-11-2013, 08:53 PM   #1
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335 with MT gets better MPG than auto?

BMW states the MPG of the 335i MT is rated at 20/30 (23 overall), and the 8AT is rated at 23/33 (26 overall). However, I've been pleasantly surprised at the fuel economy I've been getting with my own 335i M-sport MT: 25-26 MPG (calculated manually, about 75% highway, mostly comfort mode with a smattering of Ecopro and sport/sport+). Based on data reported in MPG-related threads here and on Fuelly, it seems like many other MT drivers are getting similar results.

Supposedly, the 8-speed auto is amazingly adept at finding the perfect gear to maintain efficiency, while in contrast the MT of the 335 suffers from close ratios, two less gears, and an antiquated shifting control mechanism (i.e. a human being).

So my question is, how is it that the MT seems to be getting very close to and often better numbers than the 8AT? Various hypotheses:

1. The efficiency of the 8AT is overrated.
2. The efficiency of the 335 MT is underrated.
3. Selection bias. The people living in big cities with dense traffic go with the auto; and bad traffic = poor MPG.
4. MT owners are by nature more conscientious drivers.
5. Most young bucks don't even know how to drive a stick any more. Thus, the people who do know how to drive a stick and who still enjoy it are middle-aged guys. . . . but their testosterone levels are dropping precipitously (i.e. "low T"), and so even though they fancy themselves as still young and hip and exciting in their sporty BMWs, in reality, they just don't drive that fast any more.

Thoughts?
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      03-11-2013, 09:07 PM   #2
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Your logic is lost here.
Your got better mpg than BMW's estimation just means BMW gives their number conservatively. Same thing happens on 8 AT.
Simply because you got better mpg on manual compared with its book number and you think mpg of AT is overrated? Where this logic come from?
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      03-11-2013, 09:54 PM   #3
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Quote:
Originally Posted by Nepal View Post
Your logic is lost here.
Your got better mpg than BMW's estimation just means BMW gives their number conservatively. Same thing happens on 8 AT.
Simply because you got better mpg on manual compared with its book number and you think mpg of AT is overrated? Where this logic come from?
I presume you did not read the entirety of my post. Yes, I said that in my own experience, my mpg exceeded the values estimated by BMW. And you're right, it would be illogical to use only that one reference point to try to prove my argument. As my old high school chemistry teacher said, "do not extrapolate beyond your data points." But if you read my post carefully, I said that there are other sources of data that show the same trend. For instance, the data reported in threads such as the one titled "Real world MPG?", and the data in Fuelly.

For instance, if you check out the Fuelly website, here are some examples from the 2013 335 people:

My Machine (auto): 24.9 mpg (worse than BMW estimate)
Judith (manual): 24.4 mpg (better than BMW estimate)
Bimmer (auto): 26.7 mpg (better than BMW estimate)
Blueberry (manual): 16.8 mpg (worse than BMW estimate)
AW M335i (manual): 24.5 mpg (better . . .)
BMW 335i (auto): 23.3 (worse . . . .)
F30 335i (manual): 25.5 (better. . . )
Blue Balls (manual): 25.3 (better . . . .)

So there you have it. (4/5) of the MT beat the estimates, (1/5) did worse. In contradistinction, for the AT people, only (1/3) did better, while the majority (2/3) did worse.

I will grant you that this is an extremely small sample size, and I am by no means trying to turn this into a bulletproof research analysis. I could quote other sources of data, but that would be excessively exhaustive. Mainly, I am just proving my point that my logic is not "lost," and it is in fact, quite sound.

I have to also acknowledge that the phrasing of my title was primarily meant to be provocative and stimulate conversation. In reality, I get the sense the 8AT would probably slightly edge out the MT in a real world analysis--but I think it would be very close. . . . much closer than the 3 mpg difference reported by BMW.

The crux of my argument is that the MT performs much better than advertised, and the 8AT appears to do worse. Why? That's what I was hoping some other people would chime in about. But if you think I'm just flat out wrong, show me some convincing data that proves it.
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      03-11-2013, 09:58 PM   #4
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I get better city than advertised in every day driving and slightly better when I go the speed limit on the highway. If I drive more than 75mph, I get a bit under the 33, obviously the faster I go the less I get. 82mph seems to get about 31mpg while 75mph gets 34mpg.

The road I normally drive on long stretches on the hwy is kinda hilly, so one could expect more on a flat road.

I should say my car has the auto and my driving is mostly city. As you can see in my sig, I'm a shade under 27mpg with about 70% city.

Last edited by tdizzle; 03-11-2013 at 10:03 PM.
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      03-11-2013, 10:11 PM   #5
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I think your logic is solid. I've always argued that MT is more efficient if driven properly. I especially agree with 4 and sadly 5.
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      03-11-2013, 10:24 PM   #6
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Quote:
Originally Posted by tdizzle View Post
I get better city than advertised in every day driving and slightly better when I go the speed limit on the highway. If I drive more than 75mph, I get a bit under the 33, obviously the faster I go the less I get. 82mph seems to get about 31mpg while 75mph gets 34mpg.

The road I normally drive on long stretches on the hwy is kinda hilly, so one could expect more on a flat road.

I should say my car has the auto and my driving is mostly city. As you can see in my sig, I'm a shade under 27mpg with about 70% city.
Nice work! I think your numbers are on the higher end for most 335s in general. Regardless of the transmission, I think BMWs achieve remarkable fuel efficiency, especially in light of the performance. The fuel efficiency was a leading factor in my choice of a 335 over the S4.

Still, I'm perplexed why the MT numbers are (on average) much better than the BMW estimates.

It's interesting to see the mpg/speed you report. I'll check on the way to work tomorrow, but I suspect my car computer will report less than 31 mpg at 82 mph. Logically, I would think the 8th gear of the auto would give an advantage over the MT's 6th gear at those higher speeds.
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      03-11-2013, 11:03 PM   #7
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      03-11-2013, 11:21 PM   #8
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Can we just have the usual 335i vs. 328i in-fight?

And, you're logic is flawed. If your driving 75% highway, you're not going to see much difference between AT vs. the MT.

As far as MPG goes for a person that is on the highway 75% of the time, the type of transmission is mostly a distinction without much a difference.
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      03-11-2013, 11:51 PM   #9
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Quote:
Originally Posted by Jackson743 View Post
Can we just have the usual 335i vs. 328i in-fight?

And, you're logic is flawed. If your driving 75% highway, you're not going to see much difference between AT vs. the MT.

As far as MPG goes for a person that is on the highway 75% of the time, the type of transmission is mostly a distinction without much a difference.
You claim my logic is flawed but you just unintentionally contradicted yourself by supporting the entire basis of my argument.

In essence, I'm saying the mpg difference for the 335 MT and AT is minimal, yet BMW says otherwise.

You said, " if [you're] driving 75% highway, you're not going to see much difference between AT vs. the MT." That's exactly my point!!! So then why does BMW say my MT will get 3 mpg less (30 vs. 33 for hwy)?

Also, I hate to reiterate myself, but your argument doesn't account for all the other variety of driving conditions of 335 owners that I alluded to (such as in Fuelly). Surely some of them do more city driving.
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      03-12-2013, 12:03 AM   #10
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I know some people are probably sick of all these mpg threads, but this particular point I'm emphasizing about the 335 MT vs. AT was a very big deal to me when I was buying my car. I really wanted the manual but the purported 3 mpg advantage of the auto was a major selling point that almost convinced me to change my mind.

Now, after owning a manual, and ALSO reading about other people's experiences, I think the mpg numbers that BMW reports are totally misleading. Maybe the average BMW owner doesn't care that much about 3 mpg, but I think there are a few other people besides myself for whom that is a fairly significant number. Knowing that there really isn't much of a difference between the two might help some future owners feel better about getting the MT (if that's what they like--the auto is great too ).
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      03-12-2013, 12:13 AM   #11
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Quote:
Originally Posted by Jackson743 View Post
Can we just have the usual 335i vs. 328i in-fight?

And, you're logic is flawed. If your driving 75% highway, you're not going to see much difference between AT vs. the MT.

As far as MPG goes for a person that is on the highway 75% of the time, the type of transmission is mostly a distinction without much a difference.
Firstly, please note the bolded words. Do not try to prove somebody else wrong unless you are perfect yourself.

Secondly, the freeway is the only place where the 8-speed auto will (theoretically) lead to better gas mileage due to its longer gearing.
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      03-12-2013, 01:57 AM   #12
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Quote:
Originally Posted by Mahzari View Post
Firstly, please note the bolded words. Do not try to prove somebody else wrong unless you are perfect yourself.

Secondly, the freeway is the only place where the 8-speed auto will (theoretically) lead to better gas mileage due to its longer gearing.
I Agree... My friend has a Lexus IS-F with an 8 Speed auto and it gets much better mileage on the highway.... he gets around 21-22 mpg which is pretty good considering its a V8 engine... i am sure the tranny makes a huge difference

Last edited by jz_sax; 03-12-2013 at 03:30 AM.
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      03-12-2013, 03:30 AM   #13
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Not disputing your results, but your sample size is too small and can't account for people's driving habits regardless of whether they give a percentage of city vs highway.

A conservative driver can typically exceed EPA estimates. If you drove a 8AT in the same manner, you'd likely get even better mileage. It wasn't too long ago that MT got better mileage than automatics, but even then the difference was very small.
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      03-12-2013, 04:40 AM   #14
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Quote:
Originally Posted by MadZarBMR View Post
I think your logic is solid. I've always argued that MT is more efficient if driven properly.
This.

If you know how to drive stick efficiently (eco-driving and what-not) then it will most certainly outperform the AT since that has a torque converter and other components with typically lowers mpg.
I have once gotten 69 mpg highway with my manual diesel, and it's advertised as 61 mpg highway. I wasn't driving faster than 60 mph.
I have also changed the correction factor to show more accurate numbers.(seemed to show about 6-7 % more mpg, no more)
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      03-12-2013, 05:02 AM   #15
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Quote:
Originally Posted by Anonymous Henchman #5 View Post
I know some people are probably sick of all these mpg threads, but this particular point I'm emphasizing about the 335 MT vs. AT was a very big deal to me when I was buying my car. I really wanted the manual but the purported 3 mpg advantage of the auto was a major selling point that almost convinced me to change my mind.

Now, after owning a manual, and ALSO reading about other people's experiences, I think the mpg numbers that BMW reports are totally misleading. Maybe the average BMW owner doesn't care that much about 3 mpg, but I think there are a few other people besides myself for whom that is a fairly significant number. Knowing that there really isn't much of a difference between the two might help some future owners feel better about getting the MT (if that's what they like--the auto is great too ).
I know your revised official test regime in the US reflects fuel consumption more accurately than ours does over here in Europe, but surely you still have to take them with a 'pinch of salt' anyway, as they are comparison tests in controlled conditions and not truely reflective of each driver's city and highway mix, or driving style. So there will be variations and some will feel they are doing well, while others will be disappopinted.

I've looked at the mpg figures reported over here in the UK, for the BMW models with the option of the 8-speed auto, on one of our motoring sites, Honest John's Real MPG. I've been watching the trend as fuel consumption reports have been added. There is no clear pattern emerging at all, for whether the gearbox is better than manual for mpg or not. Some models show an advantage to the auto, some to the manual. That can apply to engine types and capacity in different models as well. So we come back to all the variables, rather than the official part being unrepresentative of real world mpg, auto or manual, (other than all cars typically have an mpg shortfall against the official 'controlled' regime).

I still believe each driver has quite an impact on what he or she achieves in mpg, whatever the official figures, whatever the gearbox. Hence the mpg mix we see reported. We still get a few unusual examples here in the UK, where official figures don't crossover well to real world driving, usually where engine size in a particular model favours (or not) the official figures. So we get economy cars which fall way below the official figures in real world driving, and some thirsty cars which exceed the figures quite easily.

Typical examples used to be smaller diesel autos would fall way short, big petrol autos would exceed the figures. That has all changed with the latest designs and 8-speed autos as that pattern no longer shows up the same, even with our flawed EU official test regime, compared against real world figures. 8-speed autos appear to have changed the real world consumption mix from my observations.

I do believe the driver who wants to eke out the best mpg is best suited to a manual gearbox, assuming the car is driven to that goal. But even then it isn't as it used to be, as some old style economy techniques are not suited to the way engines are mapped these days. I was driving a manual car the other day with a gearchange indicator. I tried some typical economy driving tricks, but the car was telling me to be in a lower gear which surprised me. This is not uncommon, was reading an article where this very subject was being discussed, other economy drivers have found the same, engine mapping can mean more revs than we would normally apply as a manual driver.

Hence why driving an 8-speed auto these days and letting it do its thing may well be the economy drive, compared to the MT driver who is out of phase with the latest mapping for economy.

Sorry for rambling....

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      03-12-2013, 05:49 AM   #16
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FWIW, here is another perspective. I have noticed that when I drive the 335i 6MT mostly in comfort in roughly 1/2 city and 1/2 HW over the course of a week commute, I get slightly better MPG than I did in my old E46 325i 5MT. However, if I drive mostly in sport/sport +, the MPG takes a noticable hit and i have to fill up a day or 2 sooner. I have not run any hard calculations (in part because I do not have that kind of time on my hands
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      03-12-2013, 08:12 AM   #17
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Quote:
Originally Posted by Fille View Post
This.

If you know how to drive stick efficiently (eco-driving and what-not) then it will most certainly outperform the AT since that has a torque converter and other components with typically lowers mpg.
I have once gotten 69 mpg highway with my manual diesel, and it's advertised as 61 mpg highway. I wasn't driving faster than 60 mph.
I have also changed the correction factor to show more accurate numbers.(seemed to show about 6-7 % more mpg, no more)
The torque converter on the Steptronic is only used to provide smooth starts. Once the car is moving it is locked up via a clutch type mechanism. It will have no effect when the car is cruising on a highway in top gear.

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      03-12-2013, 08:19 AM   #18
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It's pretty obvious what the explanation is, you're driving your 300 hp car like a Camry, which gives you better numbers than BMW, who estimates an average person who drives neither slow nor fast.
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      03-12-2013, 08:29 AM   #19
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Quote:
Originally Posted by Anonymous Henchman #5
BMW states the MPG of the 335i MT is rated at 20/30 (23 overall), and the 8AT is rated at 23/33 (26 overall). However, I've been pleasantly surprised at the fuel economy I've been getting with my own 335i M-sport MT: 25-26 MPG (calculated manually, about 75% highway, mostly comfort mode with a smattering of Ecopro and sport/sport+). Based on data reported in MPG-related threads here and on Fuelly, it seems like many other MT drivers are getting similar results.

Supposedly, the 8-speed auto is amazingly adept at finding the perfect gear to maintain efficiency, while in contrast the MT of the 335 suffers from close ratios, two less gears, and an antiquated shifting control mechanism (i.e. a human being).

So my question is, how is it that the MT seems to be getting very close to and often better numbers than the 8AT? Various hypotheses:

1. The efficiency of the 8AT is overrated.
2. The efficiency of the 335 MT is underrated.
3. Selection bias. The people living in big cities with dense traffic go with the auto; and bad traffic = poor MPG.
4. MT owners are by nature more conscientious drivers.
5. Most young bucks don't even know how to drive a stick any more. Thus, the people who do know how to drive a stick and who still enjoy it are middle-aged guys. . . . but their testosterone levels are dropping precipitously (i.e. "low T"), and so even though they fancy themselves as still young and hip and exciting in their sporty BMWs, in reality, they just don't drive that fast any more.

Thoughts?
no... you should also drive the auto in the same manner with controlled variables in order for you to come up with a conclusion based on your driving pattern and habits. If I were to drive a manual I am sure that I am going to get worse mileage than auto.
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      03-12-2013, 08:38 AM   #20
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In Eco-Pro mode it gets better, but only by 10-15% (which is what BMW advertised). With manuals, it's all about the driver. I'm trying my hardest to drive economical while fighting the urge to surge after every stop light. My last run on full Eco-Pro (as in the whole week) I got about 25MPG, which is 2 better than my average of 23. I do drive about 70% city, so I'm getting decent gas mileage IMO.
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      03-12-2013, 09:25 AM   #21
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This thread seems to be more of a rant by the OP about his hate for auto drivers than a factual explination of why one gets better MPG than the other. FYI OP, I'm a diehard manual driver, but I chose the auto for my 328 since I commute in it.

Here are the facts:

The torque converter point is moot, due to the fact that it is locked almost immediatley.

- The 8th gear ratio of the auto is .667, and 6th in the manual is .846

- The final drive ratio of the auto is 3.154, and the manual is 3.231.

So OP, how on earth, if you drove the exact same commute with the same driver, in both a manual and automatic version of the same car, could the manual get better fuel economy? Not only does the EPA rating dispprove your theory, but factual info does. There is no way you would get better milage in a car with higher final drive and higher highway gearing.

Last edited by rohms3; 03-12-2013 at 10:12 AM.
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      03-12-2013, 09:29 AM   #22
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Quote:
Originally Posted by smohr33 View Post
So OP, how on earth, if you drove the exact same commute with the same driver, in both a manual and automatic version of the same car, could the manual get better fuel economy? Not only does the EPA rating dispprove your theory, but factual info does. There is no way you would get better milage in a car with higher final drive and highway gearing.
It's been many years since I owned a MT, but I always assumed those with very good 6MT mileage achieved it via an abnormal amount of coasting while in not in any gear (neutral).
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