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General E46 Forum
This is the place to get answers, opinions and everything you need related to your E46 (sedan, coupe, convertible and wagon) BMW!

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Old 04-08-2012, 01:57 AM   #21
MercForHire
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Originally Posted by shanneba View Post
The Car will adapt to changes in octane AS LONG AS THE Knock Sensors are working. If there is an issue with them the car will default to ignition timing map for 91 RON octane.

Our US Octane ratings are R+M/2 or the average of the Research and Motor octanes. (91 RON is about the same as 87 AKI used in the US)
http://en.wikipedia.org/wiki/Octane_rating

http://www.bmw-planet.com/diagrams/r.../e46/index.htm
Self-diagnosis and emergency operation of the knock control system

Self-diagnosis of the knock control system includes following checks:
Check for sensor signal interference/line break, plug connector defective etc.
Self-test of entire evaluation circuit
Check of basic engine noise level detected by the knock sensor

The knock control system is switched off if a fault is found during the course of one of these checks. The emergency program adopts the task of controlling the ignition timing. At the same time, a defect code is stored in the defect code memory. The emergency program ensures damage-free operation as from minimum RON 91. It depends on the engine load, speed and temperature.
Great info but there have been no reports of the knock sensors malfunction yet.
If someone has so little faith in every component of their e46 and is forced to use 91 out of fear. Then please, sell the German piece of sh1t.
Quote:
http://www.e46fanatics.com/forum/sho...=568436&page=2

Hate to tell you guys this but I have been running regular gas in my car for the last 160,000 miles and yet to have a problem. MY car currently has 200,000 miles and runs like a champ. It purrs like a kitten no pinging either.

Oh by the way I get 32mpg on the highway and 24-6 in mixed driving.

I have tried premium gas weeks at a time and saw no noticeable difference in the performance or engine noise or mileage.

Anyone who says your engine will run like crap and will get horrible gas mileage is full of crraaaaaap. If you are willing to pay 15-30 cents extra per gallon to get 1-2 extra hp out of your engine by all means go ahead and spend your money. I am a car nut and I love the speed and power but if I cant feel a difference, I am not blowing my money away. If you think that your precious BMW engine is designed for 91 octane and will crap out with anything less, try going to other countries. BMW sells worldwide and you would be lucky to get a quality gas with 91 octane in other countries. BMW designs their engines to run in all countries with less than ideal gas quality. 87 octane here would be a top notch gas in some other countries.

Again you can argue until the forum database craps out but in the end I have the proof in my garage. 200,000 miles with regular gas, NO ENGINE PROBLEMS, NO KNOCKING AND GREAT PERFORMANCE SO FAR. You can't argue with facts. As far as I am concerned Premium gas is nothing but a marketing gimmick for cars less than a Porsche. It is just a way of making BMW, LEXUS, MB owners feel special. Especially when you take in the fact that Lexus and Toyota camry uses the same engine and Lexus requires premium and Camry regular.

Unless you have high compression engine, running super/turbo charger or have a chip installed Premium gas will only save you mileage by reducing the weight of your car by lighting your wallet.

I remember reading a test for Premium gas making extra 9-11hp for a Porsche 911S which has a very high compression engine. If it only makes 10hp for a 350hp car that has 11:8 compression ratio, do you really think it will add 5-10 hp in your 220hp cars? You are lucky if you get 2 hp which you can gain by getting rid 10-20 lbs of junk in your car(buy a light battery, remove junk from the truck, better remove the full spare tire) .

Last edited by MercForHire; 04-08-2012 at 01:58 AM.
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Old 04-08-2012, 02:14 AM   #22
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91 isn't even an option in Alaska and I see an awful lot of bmw's here. Apparently they don't spontaneously combust without 91

If you're really concerned about it don't peg the gas pedal while at high elevation on a hot day every time you accelerate and you'll be fine
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Old 04-08-2012, 02:17 AM   #23
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91 isn't even an option in Alaska and I see an awful lot of bmw's here. Apparently they don't spontaneously combust without 91

If you're really concerned about it don't peg the gas pedal while at high elevation on a hot day every time you accelerate and you'll be fine
High elevation reduces the octane requirement of the engine.

Higher air temperatures do raise the octane requirement.
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Old 04-08-2012, 02:19 AM   #24
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Old 04-08-2012, 02:19 AM   #25
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Great info but there have been no reports of the knock sensors malfunction yet.
If someone has so little faith in every component of their e46 and is forced to use 91 out of fear. Then please, sell the German piece of sh1t.
No mention of knock sensor failures here, but this forum probably represents less than 1% of the E46s sold

Oh and you didn't add the part about the 91 RON being equal to US 87 AKI gasoline........
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Last edited by shanneba; 04-08-2012 at 02:29 AM.
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Old 04-08-2012, 02:19 AM   #26
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Holy fuuck.
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Old 04-08-2012, 02:30 AM   #27
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Just pump any gas in it besides diesel. It will run. Not joking.
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Old 04-08-2012, 02:44 AM   #28
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Hey everyone, i just bought my 330ci a few days ago. I always had japanese cars before. BMW seems like a different language to me nowadays. My question is it says on my fuel gauge Unleaded gas ... but anyone out there using premium at all?
Smh

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Old 04-08-2012, 02:57 AM   #29
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Old 04-08-2012, 02:59 AM   #30
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No mention of knock sensor failures here, but this forum probably represents less than 1% of the E46s sold

Oh and you didn't add the part about the 91 RON being equal to US 87 AKI gasoline........
Not trying to be a b1tch but that part of the arguement is flawed.
If a problem affects 10% of all cars, then statistically 10% of users on this forum will also suffer from the problem. Regardless of the percentage of e46 owners who visits this forum.
This forum is simply a sample size, like a public survey. But since this knock sensor failure have never been mentioned here.
The probability of knock sensor failure must be so rare that we can be sure it never happens to all e46 with 99+% confidence.
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Old 04-08-2012, 04:11 AM   #31
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Not trying to be a b1tch but that part of the arguement is flawed.
If a problem affects 10% of all cars, then statistically 10% of users on this forum will also suffer from the problem. Regardless of the percentage of e46 owners who visits this forum.
This forum is simply a sample size, like a public survey. But since this knock sensor failure have never been mentioned here.
The probability of knock sensor failure must be so rare that we can be sure it never happens to all e46 with 99+% confidence.
Here are a couple of threads that show a Knock sensor code:

http://forum.e46fanatics.com/showthr...t=knock+sensor
http://www.bimmerfest.com/forums/sho...ghlight=knock+

I guess just like anything else man made, they DO fail
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Last edited by shanneba; 04-08-2012 at 10:10 AM.
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Old 04-08-2012, 09:06 AM   #32
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After running premium on the car doing a run from Chicago to Mpls. I let tank run out to just about zero miles, then filled up with Regular. Started check MPG after about 10 miles to make sure any Premium was out of the lines, I am getting 27.3 MPG instead of 28.6 driving the same roads, same conditions. The 20 cents difference in gas makes it a wash, as far as saving money.
I tried doing this "test" around town, but conditions were too erratic.
It makes sense that you would get a little more power out of the engine with premium, I was hoping it would be a little more than .954% though. I am going 77 mph with cruise on. Oddly enough, dropping the top has more of an effect on MPG (+) than using premium. I will have wait for a time when it not raining out to do that.
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Old 04-08-2012, 09:25 AM   #33
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Octane content really does not change the amount of energy stored in the fuel. What it does is raises the temperature required to ignite the fuel.

Since most cars (and all e46) come with electronic knock sensors, you are not damaging your car by going below reccomended levels. However you will experience some level of knock which will lead to reduced economy and performance.
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Old 04-08-2012, 09:34 AM   #34
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I also find it interesting that the BMW ECU and programming includes a data value that indicates to service techs what the RON value of the fuel being used is:

http://www.bmw-planet.com/diagrams/r.../e46/index.htm
Open Compete Vehicle, Drive, Engine Management MS43 ...... , symptoms, Complaints, RON Factor for determining Fuel Quality

RON factor for determining fuel quality

Fuels with a low octane number may be the cause of the following problems.
- High fuel consumption
- Reduced tractive power
- Driving operation malfunctions
- Poor start-off characteristics

The RON factor serves the purpose of determining the fuel quality used. The reference values refer to the following:
RON factor Refueled fuel quality
0 to 0.2 RON 98
0.2 to 0.6 RON 95
0.5 to 1.0 RON 91
These reference values apply at outside temperatures higher than 25 C. At lower temperatures, knocking occurs at a later point and results in lower RON factors.


I generally see this value at 0.1 - 0.2 when running 93 AKI US gas. The next time I have to get 91 octane I'll try to confirm the values I get.
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Old 04-08-2012, 10:43 AM   #35
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why are you cheap bastards even arguing about what gas to put in, just use premium, its only a few cents more and you know nothing bad will happen....damn e46 has finally fallen into the hands of those on wellfare
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Old 04-08-2012, 10:48 AM   #36
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Hey everyone, i just bought my 330ci a few days ago. I always had japanese cars before. BMW seems like a different language to me nowadays. My question is it says on my fuel gauge Unleaded gas ... but anyone out there using premium at all?
Premium or unleaded? What does that mean?

The real question is premium or regular, and the correct answer is mid-grade. Your car does not need premium (91, or 93 in some places), and will tolerate regular (87), but it runs the best on mid-grade (89).
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Old 04-08-2012, 10:51 AM   #37
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You'll be fine running regular unleaded.

If you find any leaded gas, I'm sure the EPA has a bounty out for that kind of thing.
LEADED GAS will kill the CAT. Period.
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Old 04-08-2012, 11:10 AM   #38
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LEADED GAS will kill the CAT. Period.
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Old 04-08-2012, 11:12 AM   #39
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Fuel selection is a function of economics more than anything else. No engine needs higher grades of fuel than is stated by the engineers, and they all will tolerate a lesser grade.

If you ran a test of several tanks of gas (at least 5 of each grade) and kept track of the Cost Per Mile (divide the cost per gallon by the miles per gallon), you would find that the correct grade would actually cost less than the lesser grade. Typically, the cost savings of the more expensive fuel over the course of a year will run to about $150-ish because the car will deliver better mileage, meaning you buy less fuel. The DIFFERENCE in the cost of regular and mid-grade is generally about 10 cents, but the mid-grade gives enough improvement in the performance and fuel economy that the cost per mile is actually lower.

If fuel costs $3.50 for regular and delivers 20mpg, then the cost per mile is $0.175, but if the fuel cost is $3.60 and you get 22mpg, then the cost per mile is $0.164, saving you $0.011 per mile, and if you drive 12,000 miles in a year then you would save $132 in fuel costs. If the cheap gas comes in at $0.175 per mile, then multiply the expensive gas by .175 to determine the break even point where you need to see an improved mpg to justify the expense. If the cheap gas is $3.50 and the expensive gas is $3.60, then you need better than 20.6mpg to recover the cost. Anything better than 20.6 for the cost up is fuel savings.

Sheesh, do the math.
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Old 04-08-2012, 11:44 AM   #40
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Fuel selection is a function of economics more than anything else. No engine needs higher grades of fuel than is stated by the engineers, and they all will tolerate a lesser grade.

If you ran a test of several tanks of gas (at least 5 of each grade) and kept track of the Cost Per Mile (divide the cost per gallon by the miles per gallon), you would find that the correct grade would actually cost less than the lesser grade. Typically, the cost savings of the more expensive fuel over the course of a year will run to about $150-ish because the car will deliver better mileage, meaning you buy less fuel. The DIFFERENCE in the cost of regular and mid-grade is generally about 10 cents, but the mid-grade gives enough improvement in the performance and fuel economy that the cost per mile is actually lower.

If fuel costs $3.50 for regular and delivers 20mpg, then the cost per mile is $0.175, but if the fuel cost is $3.60 and you get 22mpg, then the cost per mile is $0.164, saving you $0.011 per mile, and if you drive 12,000 miles in a year then you would save $132 in fuel costs. If the cheap gas comes in at $0.175 per mile, then multiply the expensive gas by .175 to determine the break even point where you need to see an improved mpg to justify the expense. If the cheap gas is $3.50 and the expensive gas is $3.60, then you need better than 20.6mpg to recover the cost. Anything better than 20.6 for the cost up is fuel savings.

Sheesh, do the math.
people never understood this. they always compare price at the pump rather than price down the road. but then again the majority of the population dont even know how to check engine oil.
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