Engine Knock after "Cheap" Gas Fill Up

[moveswiftly]

If you were knocking there would've been codes. Also, the car takes a few pulls to adapt to the fuel. But As others have said knock is most of the time not audible, at least in our cars.

What you are hearing is either wastegates, injectors or the engine itself. Our engines like to tick.

I'd say it's just you being paranoid.

Also even if you did put 89 it
Wouldnt harm your car immediately. Use of it over time will.

[chili555]

Originally Posted by RnmEvo9

LOL ok next time instead of filling up with that piss gas 91 octane, fill up with 87 octane and report your findings here lmao!

LYAO all you want. I am running 87 octane right now and there is no knock. Normal driving, that is going around town or on the highway at legal speeds, is perfectly normal. I haven't tried a 0-100mph drag race with some crazed tuner, but that's not my intended usage anyway. If you are using your 1-series at the track or you absolutely, positively have to win the race to the next light, well, then you need 93-octane.

IMHO there's a lot of paranoia about gas.

I agree.

If BMW printed in their own manual that it's acceptable to run 87 octane when, in fact, it's injurious to the engine, the lawyers, including mine, would slaughter them. Instead, BMW is probably the most well-respected car manufacturer in the world.

[RnmEvo9]

Originally Posted by chili555

LYAO all you want. I am running 87 octane right now and there is no knock. Normal driving, that is going around town or on the highway at legal speeds, is perfectly normal. I haven't tried a 0-100mph drag race with some crazed tuner, but that's not my intended usage anyway. If you are using your 1-series at the track or you absolutely, positively have to win the race to the next light, well, then you need 93-octane.I agree.

You have a 128i. Your engine does not care for having 93 octane.

[Tom K.]

Originally Posted by chili555

LYAO all you want. I am running 87 octane right now and there is no knock. Normal driving, that is going around town or on the highway at legal speeds, is perfectly normal. I haven't tried a 0-100mph drag race with some crazed tuner, but that's not my intended usage anyway. If you are using your 1-series at the track or you absolutely, positively have to win the race to the next light, well, then you need 93-octane.I agree.

If BMW printed in their own manual that it's acceptable to run 87 octane when, in fact, it's injurious to the engine, the lawyers, including mine, would slaughter them. Instead, BMW is probably the most well-respected car manufacturer in the world.

All very true - no damage, and you won't hear any knocking because the ECU retards the timing as necessary when using 87. But as BMW recommends and has tuned the motor for 91 octane, this timing change will cause some degradation in both performance and fuel economy.

As I'm more concerned about the latter, I use a figure of 8% (BMW quotes this as the power loss for their R1200 motorcycle when using 87 octane) and if 93 octane costs no more than 8% more than 87, I choose it on the principle that it is more cost effective.

Of course, as they say, YMMV.

Tom

[RPM90]

Originally Posted by RnmEvo9

You have a 128i. Your engine does not care for having 93 octane.

Actually, all engines "care" for having good and proper octane fuel.
Nearly all modern NA engines also have knock sensors.
For example, the NA N52 has a knock sensor.
Even a basic NA engine like Nissans 2.5 4cyl has a knock sensor.

Knock is more likely to occur in high compression engines, supercharged/turbo charged engines, highly tuned/greater timing advance engines, that's why they require higher octane fuel.

Knock can occur even in relatively low powered engines.
Having a sensor helps to keep knock events in check, as modern ECU's can adjust parameters to control it.

[RnmEvo9]

Originally Posted by RPM90

Actually, all engines "care" for having good and proper octane fuel.
Nearly all modern NA engines also have knock sensors.
For example, the NA N52 has a knock sensor.
Even a basic NA engine like Nissans 2.5 4cyl has a knock sensor.

Knock is more likely to occur in high compression engines, supercharged/turbo charged engines, highly tuned/greater timing advance engines, that's why they require higher octane fuel.

Knock can occur even in relatively low powered engines.
Having a sensor helps to keep knock events in check, as modern ECU's can adjust parameters to control it.

An N52 does not require 93 octane, which is my point. Of course he's not going to notice a performance difference with that motor on 87 octane but I guarantee he would have if he had a motor that requires premium fuel.

[x97Melbourne]

Originally Posted by Steve_in_NH

My wife accidentally filled our 128 vert with 87 octane recently. No knock at all but a noticeable drop in power. No other problems

The owner's manual says 87 is perfectly fine with the 128i. It's only the 135i that requires 89. 91 is recommended for both. FYI.

And as an update -- I called the dealer and had arranged them to pick up my car / drop off a loaner. BUT, the knocking/clicking/whatever it actually was went away after about 3 days. The guy told me to wait on bringing in the car. He also told me that he had no idea what the sound could be because 89 fuel is BMW required fuel and no knock or click should be present. He said they often use 89 is fill up the loaners (which are 328i at this dealership). What he most suspected was just a bad batch of gas, which apparently is rare but does happen.

Interesting comments....people get all riled up about their gas!!
Thank you to everyone.....great thread.

[RPM90]

Originally Posted by RnmEvo9

An N52 does not require 93 octane, which is my point. Of course he's not going to notice a performance difference with that motor on 87 octane but I guarantee he would have if he had a motor that requires premium fuel.

No it doesn't require 93, but neither does our N54/N55.
The min recommended octane for both NA and turbo BMW engine is 91.

The N52 does require premium fuel.

[BEAR-257]

Originally Posted by RPM90

No it doesn't require 93, but neither does our N54/N55.
The min recommended octane for both NA and turbo BMW engine is 91.

The N52 does require premium fuel.

That's because in some states 91 is the most you can get. Here in Carolina there is no 91, it goes from 89 to 93.

BTW: Min is just that, the least you can get away with, besides higher octane fuel in the 135 will give you better gas millage then 87 for a few bucks more a tank full.

[RnmEvo9]

Originally Posted by BEAR-257

That's because in some states 91 is the most you can get. Here in Carolina there is no 91, it goes from 89 to 93.

BTW: Min is just that, the least you can get away with, besides higher octane fuel in the 135 will give you better gas millage then 87 for a few bucks more a tank full.

And you won't sacrifice performance. If you fill up with midgrade fuel on both, I'd guarantee you would feel a performance loss on the 135i more than a 128i.

[blue2fire]

Originally Posted by RnmEvo9

An N52 does not require 93 octane, which is my point. Of course he's not going to notice a performance difference with that motor on 87 octane but I guarantee he would have if he had a motor that requires premium fuel.

You must be kidding. I once tried a loaner 328 and was extremely disappointed with the speed, it actually felt more sluggish than a Civic, i later discovered that it was probably due to the crap fuel (probably cheapest grade), one fill up and it returned to a semblance of being able to keep up although still so-so (probably due to AT).

P.S: I did gift the next guy some 87 while returning it.

[ErvGotti]

Slightly off topic, but I had the chance of filling up with ethanol free 93 octane gas and man I was getting 4 mpg's better. It was 10 cents more than other stations in the area but 4 mpg's better at 13 gallons equal 52 more miles for a dollar more. If any of you have the chance to get this I highly recommend it. On a side note throttle response seemed better also, but overall power seemed the same.

[Tom K.]

Originally Posted by ErvGotti

Slightly off topic, but I had the chance of filling up with ethanol free 93 octane gas and man I was getting 4 mpg's better. It was 10 cents more than other stations in the area but 4 mpg's better at 13 gallons equal 52 more miles for a dollar more. If any of you have the chance to get this I highly recommend it. On a side note throttle response seemed better also, but overall power seemed the same.

Are you certain the 4 mpg improvement was under the same conditions? As pure ethanol has approximately 66% of the energy of gasoline, the E10 normally exacts a 3.4% penalty in gas mileage - all other things being equal. If that 3.4% represented a 4 mpg improvement, then you were getting better than 100 mpg to start with!

http://www.ehow.com/facts_5882696_ef...s-mileage.html

Tom

[ErvGotti]

Originally Posted by Tom K.

Are you certain the 4 mpg improvement was under the same conditions? As pure ethanol has approximately 66% of the energy of gasoline, the E10 normally exacts a 3.4% penalty in gas mileage - all other things being equal. If that 3.4% represented a 4 mpg improvement, then you were getting better than 100 mpg to start with!

http://www.ehow.com/facts_5882696_ef...s-mileage.html

Tom

Same conditions. I drove from Ohio to Florida on mostly Shell V power and averaged about 28 MPG at 70 MPH with cruise control. When I found this gas station in Florida I made it a point to get most of the V power out and filled up with 13 gallons of it. I got 31.5 MPG's on the same route I took back home, kind of just rounded it up to 4. It was 85+ out both times, humid as hell, on the same strech of road with the cruise control doing most of the work.

"Ethanol has 34 percent less energy than gasoline per gallon, which equates to about 2 to 3 miles per gallon for E10" Quoted from the site you posted. Seeing as you could get 2-3 according to them, I dont see how 3.5 to 4 is impossible.

[RPM90]

Originally Posted by BEAR-257

That's because in some states 91 is the most you can get. Here in Carolina there is no 91, it goes from 89 to 93.

BTW: Min is just that, the least you can get away with, besides higher octane fuel in the 135 will give you better gas millage then 87 for a few bucks more a tank full.

Yes, I agree, but I wasn't saying otherwise.

The NA 3.0 also requires "premium" 91 minimum. That was the point.
It too will offer a bit of extra performance on 93, just like the x35i engines,
if the ECU is tuned to perform it's best on 93, then that is the fuel that will give it optimal performance.

In your case, you should be using 93.
You can use 89 and the ECU will handle it just fine.
As with any octane grade fuel, if the quality of the fuel is good, the ECU will adjust parameters, and thus performance, to accommodate.
If the fuel is bad, like perhaps too much condensation built up in the stations tank, then even 93 would cause an engine to act up.

[RPM90]

Originally Posted by RnmEvo9

And you won't sacrifice performance. If you fill up with midgrade fuel on both, I'd guarantee you would feel a performance loss on the 135i more than a 128i.

You will only feel a performance loss IF the engine is experiencing knock.
If it's not, then performance will be the same.

Again, the performance degradation occurs only when the ECU detects a knock and must then retard timing to control it.
So, there is more likely a chance of that occurring in a turbo engine than an NA engine. It can still occur in both, and it can occur even if you are using the min or max octane for the engine.
Knock events can occur during high load and/or high heat runs.
Still, once the knock is detected and then controlled, the ECU keeps advancing timing, and power, back up until it needs to bring it back down.

You're not going to experience a performance loss just because you fill up with lower octane. Something has to happen before the engine compensates.
You've got part of correct, but it seems you're missing why it may happen.

As far as which engine will feel it more, well that's just a guess unless you put both on a dyno and create knock events to test for changes.

As a guess, let's consider a 20% percent power loss when knock is detected. 20% power loss in either engine, as that keeps it at the same level for either engine.
I can't think of a reason for why it wouldn't be the same percentage loss, but again, this is just for the thought exercise.
So, the 135i may actually experience a greater loss of power and feel as 20% for 300hp is 60hp, and for 230hp it's 46hp.
Torque loss would be even greater for the 135i at 60lb ft for the 135i, and only 40lb ft for the 128i.

It would be interesting to see actual dyno's showing some real numbers, and then have those cars driven so that drivers could report what they feel.

[RPM90]

Originally Posted by ErvGotti

Same conditions. I drove from Ohio to Florida on mostly Shell V power and averaged about 28 MPG at 70 MPH with cruise control. When I found this gas station in Florida I made it a point to get most of the V power out and filled up with 13 gallons of it. I got 31.5 MPG's on the same route I took back home, kind of just rounded it up to 4. It was 85+ out both times, humid as hell, on the same strech of road with the cruise control doing most of the work.

"Ethanol has 34 percent less energy than gasoline per gallon, which equates to about 2 to 3 miles per gallon for E10" Quoted from the site you posted. Seeing as you could get 2-3 according to them, I dont see how 3.5 to 4 is impossible.

That quote was showing the percentage of pure 100% ethanol, which we don't have for street vehicles.
E85 is the highest concentration with 85% ethanol and 15% gasoline.
That article can be misleading.

I believe TomK was getting at the percentages between the fuels to get his percentage.
The % comparison is between pure 100% ethanol to 100% gasoline.
34% less energy in 100% ethanol compared to 100% gasoline.
Pure 100% ethanol = 34% less energy than 100% gasoline.

Typical gasoline at most stations E10, contains 10% ethanol:
90% gasoline + 10% ethanol = typical pump gas E10
10% ethanol that has 34% less energy is
10% of 34% = 3.4%

Example:
100% gasoline averages 30mpg in Vehicle A
100% ethanol averages 34% less energy = 19.8mpg in Vehicle A

100% E10 (90% = 27mpg)
10% ethanol which is 34% less of 3mpg (10% of 3mpg = 1.98mpg)
27 + 1.98 = 28.98mpg using E10 in Vehicle A, which is 3.4% less mpg compared to 100% gasoline.

Wind conditions, windows open/closed, AC cycling, and even the number of cars and trucks ahead and behind could make a difference.
Even though some of those things are small, on a long trip they can add up.
Have you driven this route there and back using the same type of fuel?
You'd probably see an MPG difference even when using the same fuel.

[ErvGotti]

Originally Posted by RPM90

That quote was showing the percentage of pure 100% ethanol, which we don't have for street vehicles.
E85 is the highest concentration with 85% ethanol and 15% gasoline.
That article can be misleading.

I believe TomK was getting at the percentages between the fuels to get his percentage.
The % comparison is between pure 100% ethanol to 100% gasoline.
34% less energy in 100% ethanol compared to 100% gasoline.
Pure 100% ethanol = 34% less energy than 100% gasoline.

Typical gasoline at most stations E10, contains 10% ethanol:
90% gasoline + 10% ethanol = typical pump gas E10
10% ethanol that has 34% less energy is
10% of 34% = 3.4%

Example:
100% gasoline averages 30mpg in Vehicle A
100% ethanol averages 34% less energy = 19.8mpg in Vehicle A

100% E10 (90% = 27mpg)
10% ethanol which is 34% less of 3mpg (10% of 3mpg = 1.98mpg)
27 + 1.98 = 28.98mpg using E10 in Vehicle A, which is 3.4% less mpg compared to 100% gasoline.

Wind conditions, windows open/closed, AC cycling, and even the number of cars and trucks ahead and behind could make a difference.
Even though some of those things are small, on a long trip they can add up.
Have you driven this route there and back using the same type of fuel?
You'd probably see an MPG difference even when using the same fuel.

Let me put the full quote on that "Ethanol has 34 percent less energy than gasoline per gallon, which equates to about 2 to 3 miles per gallon for E10 (10 percent ethanol), according to the New York Times.

Either way you look at it if your getting at a minimum 2 mpg's better for 10 cents a gallon more in a 13 gallon tank that equate's to 26 more miles for $1.30. So if your average MPG's is say 26 MPG's your getting a gallon of gas for $1.30 and at the current prices you cant beat that.

I'm not fighting the math I'm just reporting what I was getting according to the ECU. To me conditions couldn't have been more perfect to test as far as temps, winds, same route, and cruise control set to 70 in 6th gear. I tried my best to replecate the conditions and that was the outcome.

[RPM90]

Originally Posted by ErvGotti

Let me put the full quote on that "Ethanol has 34 percent less energy than gasoline per gallon, which equates to about 2 to 3 miles per gallon for E10 (10 percent ethanol), according to the New York Times.

Either way you look at it if your getting at a minimum 2 mpg's better for 10 cents a gallon more in a 13 gallon tank that equate's to 26 more miles for $1.30. So if your average MPG's is say 26 MPG's your getting a gallon of gas for $1.30 and at the current prices you cant beat that.

I'm not fighting the math I'm just reporting what I was getting according to the ECU. To me conditions couldn't have been more perfect to test as far as temps, winds, same route, and cruise control set to 70 in 6th gear. I tried my best to replecate the conditions and that was the outcome.

I understand that you saw an increase in MPG, and of course there is no dispute on what MPG you got.

But, the math and science are important, and thus getting the numbers correct is important.
Experiences like your are anecdotal, relevant to your instance.
But, is it definitive?
I don't see how it can be as there are no other vehicles on that trip to test same conditions and fuel, as well as no control vehicle that didn't change fuel, so that we can see if other factors were at play.


"Ethanol has 34% less energy than gasoline PER GALLON...."

"...which equates to about 2 to 3 miles per gallon for E10..."
That's the confusion part, as it's not making a clear and equal comparison.
If the difference is in percentage, then how did they come up with the "2 to 3 mpg" number?
As a percentage, the actual MPG will vary depending on the vehicles base/avg MPG, thus the actual MPG will be different on different vehicles as it's a percentage difference not an actual MPG number.

If a vehicle is getting 20mpg on 100% gasoline, then on E10 with 10% ethanol it will get 3.4% less MPG, or 19.32MPG, a difference of less than 1 mpg.
If a vehicle is getting 40mpg on 100% gasoline, then it will get 3.4% less MPG on E10, which is 38.64MPG, a difference of 1.36 mpg.

Here's an interesting article:
http://www.ethanol.org/pdf/contentmg...yStudy_001.pdf

Note that it is research done by a pro ethanol group.
But the test seems sound.

There are other sites that make all kinds of MPG claims using E10.
Some have even claim a reduction up to 20%!
http://www.fuel-testers.com/MPG_gas_...0_ethanol.html

This is why anecdotal "evidence" requires suspicion.