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Old 03-29-2020, 03:24 PM   #21
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There is no need to turn a car off and back on if you sit less than 2-3 minutes, it simply wastes gas and may potentially burn out the starter. If you get 13MPG, you are either driving too aggressive, not traveling long enough to warm up and operate at an efficient rate. If you haven't thrown codes yet I bet you have mayo developing under the oil fill cap.
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Old 03-29-2020, 03:42 PM   #22
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it simply wastes gas
starting an electronically fuel injected engine that is already at OP temp does not waste more gas than having the engine idling for 2-3 minutes.
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Old 03-29-2020, 04:03 PM   #23
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My overall average is about 20 mpg according to the Fuelly app. I do mostly short trips around town and between nearby towns under 10 miles away. Last one was 17.4 mpg but my mph is higher, I think that's the OP's issue. He needs to take a 50 mile road trip with all highway miles and then post those numbers.
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Old 03-29-2020, 04:20 PM   #24
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Extra wear on the starter? Sure. Any moving part has a life cycle that is reduced when it's moving or used. The starter is no different. On top of that, the starters in auto on/off cars are specifically designed to be used an absurd amount of times. But look, plenty of people are STILL on their original starters at 20 years and 200+ thousand miles, they aren't super fragile items. Using it a few extra times per drive will accelerate wear, but again, if you aren't doing it every other minute down the road it's really not that big of a deal. There is no warning in the manual saying, be careful doing quick trips to multiple different stores because your starter will explode!!! Just don't do it at every 30 second traffic light all day every day. That way, yes, will drastically accelerate wear on the starter.
i hear what you're saying.
but you can't really use years/miles to how much use a starter has on it. it's how many times it's used to start, and someone with 10,000 miles could use it as much as someone with 200,000.

and having to use more for just stop-starts can shorten it's life ten fold because of the increased use.

higher compression engined M3s seem to eat starters a lot.
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Old 03-29-2020, 05:43 PM   #25
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Just as a data point:
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Old 03-29-2020, 07:11 PM   #26
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Just for another data point: I was getting 16-17 mpg in town. Changed the brake booster and in town MPGs went back to 20-21.

Booster was probably the greatest source of vacuum leaks for me. Ymmv.


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Old 03-29-2020, 07:49 PM   #27
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Just as a data point:
]
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Old 03-29-2020, 11:17 PM   #28
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Im getting about 18 mpg mixed city/highway on my XI, which weighs a noticeable bit more. Im not much of an economical driver myself, I usually touch redline a couple times a day. Try dumping a bottle of BG44k or techron into the tank next time and drive it hard. After that tank of cleaner you should gain some MPG from the injectors being cleaned. I myself gained about 3-4 MPG which is a pretty hefty increase, and my fuel level reads correctly at startup now since it cleaned the sensor in the tank off. I do techron every couple thousand miles, usually just grab it whenever im at the parts store and its on sale. Before using fuel cleaner I was getting 12 mpg, which is just pitiful.

Stop/start is stupid technology that like most modern car tech is solely for the purpose of keeping emissions down and the EPA happy. If I ever get a car with this the first thing i'll do each time I get in is turn it off. Unnecessary wear on the starter and charging system. Dont shut off your car at lights unless you think the ~dollar of fuel you save is worth more than a ~200 dollar starter

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Old 03-30-2020, 04:31 PM   #29
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Just for another data point: I was getting 16-17 mpg in town. Changed the brake booster and in town MPGs went back to 20-21.

Booster was probably the greatest source of vacuum leaks for me. Ymmv.
Tiny vac leaks can be tricky to find, even with a smoke test. I was getting that kind of city mileage as well, and when I removed the intake manifold to change the hard coolant pipes I found that the intake mani gasket had a little chunk missing on the #2 cylinder.

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With the new intake gasket and injector o-rings, my all in mpgs went up, fuel trims came down, and engine had more response/power at lower rpms. I also started seeing 28 to 30 mpgs on long highway trips for the first time ever, when before I could not really get above 25mpg.
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Old 03-30-2020, 05:10 PM   #30
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I need to do my injector o-rings as well.


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Old 03-30-2020, 05:21 PM   #31
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Wow I didn't know so many people responded.

No vacuum leaks
Changed out hard coolant lines, complete cooling overhaul, fuel filter, fuel pump, intake boots, air filter, intake manifold gasket, camshaft sensors, MAF, all vacuum lines, OFHG and pre cat O2 sensors all within past 3-4 years. I drive less than 1000 miles per year. 228K on odometer right now.

I dont drive much. Mostly 5 miles one way to work and 5 miles back. Freeway going and side road coming back. I I this is a big problem.

I dont really drive much with this car. When I have resettled the MPG and gone on the freeway, it goes as high as 27 MPG. Over time it settles at 15 as I do both freeway and side road.

What perplexes me is that at fillup the remaining gas mileage is around 320 miles. I never get anywhere near that.

I also dont have a lead foot. I always monitor the analog MPG and try to keep it between 20 and 30.

I will fill up tomorrow and tell you how many MPGs I've gotten from it this time.



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Old 03-30-2020, 08:03 PM   #32
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First - are you resetting the the MPH and MPG when you fill the tank? That's the only way I have ever been able to get the On Board Computer to match the real number I calculate from the trip odometer/gallons boarded. I have never seen an explanation of the math/averaging BMW uses if you don't reset it. As far as the mileage you are seeing - that is exactly what I get in the winter some tanks when I never drive more than 5 minutes and the engine never gets warm. That plus the 1990's GM slush-a-matic in these cars is a real mileage killer in stop and go around town driving. And my car is perfectly tuned. On the highway with the cruise control set at 78 MPH I'll see 30 to 32 MPG.
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Old 03-30-2020, 08:06 PM   #33
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Age old problem, IGNORE everyone's comments about the fuel economy they are getting on their cars. They are not driving your car under your driving conditions.

Simple way to put this issue to bed, FORGET about MPG and FOCUS on Average MPH. Average MPH per tank full will pretty much tell us if you "really" have a fuel consumption problem.

What is your typicaly distance you drive each time you start the engine, this is also critical to understand.

Your profile indicates you live in CA, chances are you are in a major city in CA, LA, SF, San Jose or some other metro area. You probably have a short commute and/or spend 40-50 minutes going 5-7 miles. The engine and engine oil probably never has enough run time to fully warm up, one more critical factor that can kill fuel economy.

Understand this one critical point that is overlooked ALL THE TIME. When the car is NOT moving and the engine is running/idling, you are Averaging EXACTLY 0/ZERO MPG. Averaging in 0/ZERO MPG into any other driving conditions will KILL any expected fuel economy.

My E46 crawled amoungst many traffic lights, stop signs and bumper to bumper traffic on daily commutes in one of the top markets for rediculous traffic, Washington, DC. The typical Average MPH per tankfull of fuel on a weekly basis was around 22 MPH, if lucky. I recall the car was getting around 16-17 MPG on Average per tank of fuel. Nothing wrong with the car other than the way it was used, it never moved over 40-45 MPH IF it ever was able to move at all.

Again, at 0 MPH or while crawling in trafic the vehicle gets 0/Zero MPG or very close to it.

Think about the class you may have received a D letter grade on an exam, there was very little you could do to ever pull up the final letter grade to an A. You could inch toward a final grade of an A, but chances are you would never get the A you were looking for. Almost stastically and realistly that the one bad grade would hurt the final class grade.

Do not drive much, have a short commute, you either need a sub 1.0 Liter engine or in your case an electric car makes more sense, a car with an internal combustion engine is not your friend for the type of driving you do.
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Old 03-30-2020, 08:22 PM   #34
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First - are you resetting the the MPH and MPG when you fill the tank? That's the only way I have ever been able to get the On Board Computer to match the real number I calculate from the trip odometer/gallons boarded. I have never seen an explanation of the math/averaging BMW uses if you don't reset it. As far as the mileage you are seeing - that is exactly what I get in the winter some tanks when I never drive more than 5 minutes and the engine never gets warm. That plus the 1990's GM slush-a-matic in these cars is a real mileage killer in stop and go around town driving. And my car is perfectly tuned. On the highway with the cruise control set at 78 MPH I'll see 30 to 32 MPG.
Yes, I am resetting the MPH and MPG when I fill the tank. The freeway entrance is next to the gas station and the MPG will go up to 27. However, the trip is only 5 minutes long. After that is 5 minutes side road and the MPGs obviously plummet after that.

I heard that the immediate MPG is calculated solely off of the throttle body? That being said, not sure how tire pressure affects the sensor.


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Old 03-30-2020, 10:20 PM   #35
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Yeah, I'm relatively new the the 46 but ive never seen MPG numbers below 22 or so. Something is off with your car.
I have had 4 e46s, none of which exceeded 19.2 MPG. A huge part is where you live and type of driving. I am in San Francisco a huge portion of the time with lots of stop signs and lots of hills.
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Old 03-30-2020, 10:37 PM   #36
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I have had 4 e46s, none of which exceeded 19.2 MPG. A huge part is where you live and type of driving. I am in San Francisco a huge portion of the time with lots of stop signs and lots of hills.
That's the one thing I forgot to mention. I'm in DTLA.

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Old 03-31-2020, 10:24 AM   #37
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A large amount of salient posts here.

Fuel consumption (not MPG) is a key one. As a perfect example private airplanes measure consumption per hour. Headwind or tailwind is a large variable.
So is LA traffic vs. miles of open highway after you pass Barstow and headed toward Vegas on 15.

Start stop: I personally hate it. As a shop owner, I love it; should tell you everything you need to know.

Unless you have a BMW hybrid with the EMachine the starter is what's restarting the engine everytime you lift your foot off of the brake. The MSA system does however do a couple of things to make life a little bit easier for the starter with the MSA on (on cars so equipped) the starter. The DME takes note of what EXACT position the engine is in when it shut off the engine. When you release your foot off of the brake, the next two cylinders coming up in the firing order get a slight increase of fuel to aid the car to start quickly. Enabling shorter cranking by a few Ms for the starter/flywheel engagement time. But the starter is still working. Therefore we see cars with 50,000 miles that have starters that are somewhere in the 150-200K life.

BMW hybrids use the rather large generator located inside the large nose of the transmission bellhousing to re-start the car. Current is applied to twist the crank, and the same above scheme happens for fuel enrichment on the next two cylinders.
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Old 03-31-2020, 02:38 PM   #38
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So I just filled up. Here are the numbers:

MPG 15.3
MPH 13.7
Odomerer 126.9

Filled 8.621

126.9/8.621 = 14.72 MPG

I reset the MPG/MPH on the cluster. Got on the freeway and within 1.5 miles the MPGs were at 27 MPG. Had to get off and drive the rest via side road. Parked and at 2.7 miles since fill up. MPG on cluster is at 22.1. Mileage remaining after fill up is 343.

Does this sound about right considering my driving circumstances?

Thinking about just using this car back to once a week for long trips. Too costly for gas.

Quote:
Originally Posted by MrMCar View Post
A large amount of salient posts here.



Fuel consumption (not MPG) is a key one. As a perfect example private airplanes measure consumption per hour. Headwind or tailwind is a large variable.

So is LA traffic vs. miles of open highway after you pass Barstow and headed toward Vegas on 15.



Start stop: I personally hate it. As a shop owner, I love it; should tell you everything you need to know.



Unless you have a BMW hybrid with the EMachine the starter is what's restarting the engine everytime you lift your foot off of the brake. The MSA system does however do a couple of things to make life a little bit easier for the starter with the MSA on (on cars so equipped) the starter. The DME takes note of what EXACT position the engine is in when it shut off the engine. When you release your foot off of the brake, the next two cylinders coming up in the firing order get a slight increase of fuel to aid the car to start quickly. Enabling shorter cranking by a few Ms for the starter/flywheel engagement time. But the starter is still working. Therefore we see cars with 50,000 miles that have starters that are somewhere in the 150-200K life.



BMW hybrids use the rather large generator located inside the large nose of the transmission bellhousing to re-start the car. Current is applied to twist the crank, and the same above scheme happens for fuel enrichment on the next two cylinders.
Cool info. Thanks for sharing.

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Old 03-31-2020, 06:17 PM   #39
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Your test is not very useful.
Considering your engine is just getting up to temperature at the end of each trip.
Try mostly freeway driving for more than 5 miles, a road trip and see what you get.
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Old 03-31-2020, 07:19 PM   #40
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I have had 4 e46s, none of which exceeded 19.2 MPG. A huge part is where you live and type of driving. I am in San Francisco a huge portion of the time with lots of stop signs and lots of hills.
I hear you, I do understand your point. My e46 has 240,000 miles on it and I have had it for 6 months. My overall mpg is 29. I drive it on long trips and I live in a relatively small town. It’s a 5 speed with a new vac leak on a monthly basis, I smoke test it weekly and always find something, even after I confirm that its sealed.

The OP clearly is in a unique situation, but dang. I average almost 30 and some people average less than 20? That seems odd to me. These things are pretty sensitive as far as I can tell. How can you average less than 20MPH and enjoy a BMW? Question for another thread I guess.

Still, I am surprised that anyone averages less than 22 on a regular basis. That shocks me, but, I dont live in an urban area. Peace out.
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