[Efthreeoh]

Originally Posted by usshelena725

Um yea sure.

Just gonna leave this here. Photo of my gas tank door.

AKI is not the same octane rating as RON. AKI is an average of RON and MON octane numbers. RON is used throughout the USA as the octane rating for gasoline.

[Psyphertext]

So I ran a tank of 87 through over the past week due to getting yelled at for my fuel budget. Yikes! My fuel mileage crashed and I could tell the car didn't have the scoot it had on 91. Just because you can doesn't mean you should when it comes to fuel. As noted by others, premium car, run premium through it. Remember that if you use the fuel economy needle to guesstimate, chances are you will be off 10-20 mpg versus the digital. I run off the trip meter and this change was significant on 87 octane...As in a 40 mile loss in economy across three quarters of a tank with no out of pattern driving across 2 weeks. 09 328i with 68K on the clock, no mods. 91 got put back in this morning, so if this pattern works, it should go back up. I also buy fuel in the morning to maximize the density since fuel expands in heat and contracts in the cool.

A well known tip: If you know where your local gas station delivery trucks are getting their fuel from, you will find that many get it from the very same supply point...more often than not. That should tell you that if the supply point is the same that the only difference is the in-ground storage tanks and the pumps. Storage tanks take on water a bit too easily in the U.S. and sometimes you can tell when condensation is in the system.

Run 89 if you need cheaper fuel in the moment or tough it out with 91. Avoid 87.

[Run Silent]

Originally Posted by Efthreeoh

AKI is not the same octane rating as RON. AKI is an average of RON and MON octane numbers. RON is used throughout the USA as the octane rating for gasoline.

You really enjoy continuing to spout off data that doesn't seem to be accurate.

Please see below:

"In Europe, the octane rating on the pump is simply the RON figure. America, by contrast, uses the average of the RON and the MON figures, called the AKI (anti-knock index)."

"In most countries in Europe (also in Australia and New Zealand) the "headline" octane rating shown on the pump is the RON, but in Canada, the United States, Brazil, and some other countries, the headline number is the average of the RON and the MON, called the Anti-Knock Index (AKI), and often written on pumps as (R+M)/2"




AKI is the same thing as the Octane rating at a pump in the USA.


Sources, so you can learn something:

https://www.pei.org/wiki/octane-number

https://www.economist.com/babbage/20...-needs-premium

http://www.pencilgeek.org/2009/05/oc...nversions.html

https://en.wikipedia.org/wiki/Octane...,_MON,_and_AKI

[John 070]

Originally Posted by Psyphertext

So I ran a tank of 87 through over the past week due to getting yelled at for my fuel budget. Yikes! My fuel mileage crashed and I could tell the car didn't have the scoot it had on 91. Just because you can doesn't mean you should when it comes to fuel. As noted by others, premium car, run premium through it. Remember that if you use the fuel economy needle to guesstimate, chances are you will be off 10-20 mpg versus the digital. I run off the trip meter and this change was significant on 87 octane...As in a 40 mile loss in economy across three quarters of a tank with no out of pattern driving across 2 weeks. 09 328i with 68K on the clock, no mods. 91 got put back in this morning, so if this pattern works, it should go back up. I also buy fuel in the morning to maximize the density since fuel expands in heat and contracts in the cool.

A well known tip: If you know where your local gas station delivery trucks are getting their fuel from, you will find that many get it from the very same supply point...more often than not. That should tell you that if the supply point is the same that the only difference is the in-ground storage tanks and the pumps. Storage tanks take on water a bit too easily in the U.S. and sometimes you can tell when condensation is in the system.

Run 89 if you need cheaper fuel in the moment or tough it out with 91. Avoid 87.

Octane and mpg have no direct correlation. None. Octane is not measuring anything except qualities related to predetonation.

Some people have surmised that when lower octane fuel is used in a vehicle that can benefit from higher octane, then people's driving patterns change.

As far as fuel goes, there are only certain cos. who have their own refineries. However, that does not mean all fuel is the same.

Basically, there is branded, and unbranded, fuel. Shell, Conoco, Sunoco (oops bad example), Costco, is totally different than Wawa, Kwik E Mart, E-ZGas, Speedway, etc. The latter are all unbranded fuels. The branded fuels get their own additive packages at the terminal.

[hassmaschine]

Originally Posted by Efthreeoh

Hummmm... I had an '89 E30 for 18 years bought new in Nov. 1988. I'm positive it required high octane fuel. 91 RON. I know you still have an M20 E30 if the fuel door says otherwise then I stand corrected, but memory serves me as it required premium fuel. I'm not one to not read owner's manuals and I most explicitly follow manufacturer recommendations for everything, and I never waste money "over-buying" fuel (unless I can find non-ethanol premium for the Z3 that sits for long periods with the same tank of fuel).

Now, for my Hummer, it occasionally will get premium grade fuel just out of muscle memory of buying premium fuel for the Bimmers in the fleet...

Nope. Definitely 87. The compression ratio was only 8.8:1 - the euro cars had 9.5:1 or something and required premium. And if you got a tune, then it usually needed premium.

[atmosphericM]

Originally Posted by usshelena725

Just gonna leave this here. Photo of my gas tank door.

That black sapphire, though!

Originally Posted by Efthreeoh

Now, for my Hummer, it occasionally will get premium grade fuel just out of muscle memory of buying premium fuel for the Bimmers in the fleet...

Ouch.

[Efthreeoh]

Originally Posted by usshelena725

You really enjoy continuing to spout off data that doesn't seem to be accurate.

Please see below:

"In Europe, the octane rating on the pump is simply the RON figure. America, by contrast, uses the average of the RON and the MON figures, called the AKI (anti-knock index)."

"In most countries in Europe (also in Australia and New Zealand) the "headline" octane rating shown on the pump is the RON, but in Canada, the United States, Brazil, and some other countries, the headline number is the average of the RON and the MON, called the Anti-Knock Index (AKI), and often written on pumps as (R+M)/2"




AKI is the same thing as the Octane rating at a pump in the USA.


Sources, so you can learn something:

https://www.pei.org/wiki/octane-number

https://www.economist.com/babbage/20...-needs-premium

http://www.pencilgeek.org/2009/05/oc...nversions.html

https://en.wikipedia.org/wiki/Octane...,_MON,_and_AKI

Read what you just posted...

A number that is the average of two different numbers can't be the same value as the average; i.e. RON is not the same octane number as AKI.

[CTinline-six]

Originally Posted by Psyphertext

Remember that if you use the fuel economy needle to guesstimate, chances are you will be off 10-20 mpg versus the digital.

I hate that stupid thing. Totally useless, just swings back and forth like a pendulum every time I put my foot on the pedal.

Too bad we couldn't get something useful like I dunno a temperature gauge?

[hassmaschine]

Originally Posted by CTinline-six

I hate that stupid thing. Totally useless, just swings back and forth like a pendulum every time I put my foot on the pedal.

Too bad we couldn't get something useful like I dunno a temperature gauge?

it's an instantaneous MPG. Of course it's not going to be the same thing as the digital readout - the digital readout is a long-term average. The gauge only tells you what you're getting at that exact moment.

[CTinline-six]

Originally Posted by hassmaschine

it's an instantaneous MPG. Of course it's not going to be the same thing as the digital readout - the digital readout is a long-term average. The gauge only tells you what you're getting at that exact moment.

Yeah I knew it was instant...

Still don't see the purpose.

[Run Silent]

Originally Posted by Efthreeoh

Read what you just posted...

A number that is the average of two different numbers can't be the same value as the average; i.e. RON is not the same octane number as AKI.

Still not sure what the problem is here.

You said: "AKI is an average of RON and MON octane numbers. RON is used throughout the USA as the octane rating for gasoline."


This is incorrect. The USA and CAD do not use RON as the octane rating for gasoline when you see that number at the pump, they use AKI. When you pull up to the pump, and it says 87, 89, 91, etc - that is the AKI, not the RON.

When my fuel door says "use min 89 AKI" - it is saying to use the pump that has "89" on it at the gas station - at any location within the USA and Canada. How hard is this to understand?

So just to clarify: Your statement that says [RON is used throughout the USA as the octane rating for gasoline] is not true. The correct statement would be "AKI is used throughout the USA as the octane rating for gasoline".

[hassmaschine]

Originally Posted by usshelena725

Still not sure what the problem is here.

You said: "AKI is an average of RON and MON octane numbers. RON is used throughout the USA as the octane rating for gasoline."


This is incorrect. The USA and CAD do not use RON as the octane rating for gasoline when you see that number at the pump, they use AKI. When you pull up to the pump, and it says 87, 89, 91, etc - that is the AKI, not the RON.

When my fuel door says "use min 89 AKI" - it is saying to use the pump that has "89" on it at the gas station - at any location within the USA and Canada. How hard is this to understand?

So just to clarify: Your statement that says [RON is used throughout the USA as the octane rating for gasoline] is not true. The correct statement would be "AKI is used throughout the USA as the octane rating for gasoline".

haha. AKI *is* the average of RON and MON. It says this right on every gas pump.

That's mostly why US octane ratings are lower than europe - because MON is a "tougher" standard than RON.

[Run Silent]

Originally Posted by hassmaschine

haha. AKI *is* the average of RON and MON. It says this right on every gas pump.

That's mostly why US octane ratings are lower than europe - because MON is a "tougher" standard than RON.

I feel like I am in a twilight zone, it isn't the comment about AKI being the average that is wrong, it is the comment about the USA using RON, not AKI, that is incorrect. Good grief.

[John 070]

Originally Posted by CTinline-six

I hate that stupid thing. Totally useless, just swings back and forth like a pendulum every time I put my foot on the pedal.

Too bad we couldn't get something useful like I dunno a temperature gauge?

Isn't it a throwback to the 80's when there were cars like the 528e? I am not even convinced it means anything, is there truly calculations going on? I thought back in the day it was vacuum.

With that being said, I don't have such a needle, but, the mpg computer when compared to the pump and odo, it almost within 0.1 to 0.3 mpg, every time. BMW engineers did well here. Because I have almost never used the very same pump (implying it stops at the same point), and almost all of my gas is full service in NJ.

[hassmaschine]

Originally Posted by usshelena725

I feel like I am in a twilight zone, it isn't the comment about AKI being the average that is wrong, it is the comment about the USA using RON, not AKI, that is incorrect. Good grief.

I was agreeing with you...

[hassmaschine]

Originally Posted by John 070

Isn't it a throwback to the 80's when there were cars like the 528e? I am not even convinced it means anything, is there truly calculations going on? I thought back in the day it was vacuum.

With that being said, I don't have such a needle, but, the mpg computer when compared to the pump and odo, it almost within 0.1 to 0.3 mpg, every time. BMW engineers did well here. Because I have almost never used the very same pump (implying it stops at the same point), and almost all of my gas is full service in NJ.

It was never vacuum (maybe on VWs) - it was always calculated by the computer based on injector pulse width and other variables. How else do you think it knows your total range?

[BravoJohny33]

Originally Posted by Psyphertext

So I ran a tank of 87 through over the past week due to getting yelled at for my fuel budget. Yikes! My fuel mileage crashed and I could tell the car didn't have the scoot it had on 91. Just because you can doesn't mean you should when it comes to fuel. As noted by others, premium car, run premium through it. Remember that if you use the fuel economy needle to guesstimate, chances are you will be off 10-20 mpg versus the digital. I run off the trip meter and this change was significant on 87 octane...As in a 40 mile loss in economy across three quarters of a tank with no out of pattern driving across 2 weeks. 09 328i with 68K on the clock, no mods. 91 got put back in this morning, so if this pattern works, it should go back up. I also buy fuel in the morning to maximize the density since fuel expands in heat and contracts in the cool.

A well known tip: If you know where your local gas station delivery trucks are getting their fuel from, you will find that many get it from the very same supply point...more often than not. That should tell you that if the supply point is the same that the only difference is the in-ground storage tanks and the pumps. Storage tanks take on water a bit too easily in the U.S. and sometimes you can tell when condensation is in the system.

Run 89 if you need cheaper fuel in the moment or tough it out with 91. Avoid 87.

I have been running 87 octane for years and 60k miles. I have not experienced terrible MPG with 87

[Run Silent]

Originally Posted by hassmaschine

I was agreeing with you...

Sorry, bru. Was just so frustrated from the previous explanations that I was on edge. My apologies.

[John 070]

Originally Posted by hassmaschine

It was never vacuum (maybe on VWs) - it was always calculated by the computer based on injector pulse width and other variables. How else do you think it knows your total range?

It can't. Nobody except a fortune teller can predict the future. It is impossible for the car to know how you plan on using the remainder of the tank (stop and go, idle in the driveway at 0 mph, cruise at 72 mph, etc.)

[John 070]

Originally Posted by CTinline-six

Yeah I knew it was instant...

Still don't see the purpose.

If it were accurate, there would be a purpose. Say you are cruising along at 75 mph constantly, and it said 29 mpg. You gently step on the gas to accelerate to 80, and you see it go from 29 to 18. You would know the effect of your stepping on the accelerator. But imho it is more like you say, useless.

[gbalthrop]

Originally Posted by Efthreeoh

AKI is not the same octane rating as RON. AKI is an average of RON and MON octane numbers. RON is used throughout the USA as the octane rating for gasoline.

Originally Posted by usshelena725

...[i]"In Europe, the octane rating on the pump is simply the RON figure. America, by contrast, uses the average of the RON and the MON figures, called the AKI (anti-knock index)."... AKI is the same thing as the Octane rating at a pump in the USA.
Sources, so you can learn something:
https://www.pei.org/wiki/octane-number
https://en.wikipedia.org/wiki/Octane...,_MON,_and_AKI

Originally Posted by Efthreeoh

Hummmm... I had an '89 E30 for 18 years bought new in Nov. 1988. I'm positive it required high octane fuel. 91 RON...

Originally Posted by hassmaschine

Nope. Definitely 87.

To try to rationalize some of the discrepancies in this thread:
1) As stated above, RON is an octane rating used in Europe and much of the ROW (Rest of World), BUT, AKI is the octane rating used in the US and is the octane number appearing on the US gas pump (and also the fuel door of your US vehicle).

2) 87 AKI = 91 RON; 87 AKI (US "Regular" unleaded gas with 10% Ethanol) is the same actual octane as 91 RON, just a Different Rating system & number. See "Examples" Table in following Wiki:
https://en.wikipedia.org/wiki/Octane_rating

3) 91 AKI fuel is "highly recommended" but the MINIMUM AKI Rating is 87 for non-turbo and 89 for turbo, per the Owner's Manual:

"Required fuel

Super Premium Gasoline/AKI 91
This gasoline is highly recommended.
However, you may also use gasoline with less
AKI. The minimum AKI Rating is:
> 323i, 328i/xi: 87
> 335i: 89."

Unfortunately BMW has NOT chosen to give any clues as to WHY "Super Premium Gasoline/ AKI 91 is highly recommended." BMW or its dealers have done some some weird things to further confuse the issue. My Fuel Filler Flap has a sticker on the inside that says: "minimum octane rating (91 AKI) see Owner's Manual for details."

I have run my N52KP engine on 87 AKI since I bought it and it has performed flawlessly.

QUESTION: WOULD THE IGNITION BE MORE ADVANCED IF USE PREMIUM?

I hope we can all agree that our engines (1) have knock sensors; that (2) ignition timing is automatically retarded to prevent detonation/ knock, in certain situations, and within certain limitations; that (3) all other things begin equal (which they seldom are ;-) more power is produced in high-load, high-RPM (WOT acceleration) when ignition is more advanced; and that (4) Ignition Timing advance of #1 cylinder (Zündzeitpunkt Zylinder 1) can be read in Real Time (Parameter or Status) using INPA or other capable scan tool.

What I have NOT seen in this thread is any discussion of the the DME strategy or Algorithms for advancing/retarding spark. Also, I have NOT seen any suggestion anywhere of any alternative/ multiple "Mapped" DME strategies that can be selected determined on octane rating of the fuel that is being used.

Unless there is a way to "code" the DME to run a "timing" Map (already installed in the DME) with higher advance curve when running a higher octane fuel, then POSSIBLE DME strategies that occur to me, that allow a higher octane fuel to give better WOT (Wide-Open-Throttle) acceleration are (NOTE, these are simply SWAGS, and NOT actual knowledge):
1) There are multiple advance curve Maps in the DME, and at engine start, the DME runs the highest advance Map as default until the knock sensor signal causes it to "downshift" to a lower advance curve;
2) In certain situations, such as high-load or high-RPM, the ignition advances until knock sensor signal, and then backs off;
3) There are TWO Maps, high and low, that the DME selects one or the other depending on some algorithm which might include such inputs as: last used, knock sensor input, engine temp, load, RPM, etc.

Point is, these are all guesses, and there are other possibilities NOT included.

If there are multiple maps, or if the strategy is advance until knock, then even higher octane fuel (AvGas) MIGHT produce higher performance.

Bentley is NOT terribly helpful here, but it does state (p. 120-7):

"A knock sensor is a piezoelectric microphone
tuned to the frequencies of engine knock or detonation. If engine
knock is detected, ignition spark is retarded by the ECM. If a fault
with the knock sensor is detected the malfunction indicator light
(MIL) is illuminated"

It should be noted that Bentley suggests NO warning light, or Fault Code, will be lit on dash, or saved in DME memory, if a knock is detected, or ignition is retarded; HOWEVER a Warning Light WILL light and a Fault Code WILL be saved in DME IF there is a fault detected in the Knock Sensor circuit (wiring, connector or sensor itself).

ANYONE actually know what strategy is used in the MSV80, MSD80 or other DMEs used with N51, N52, N52KP, N54 & N55 engines? If so, please cite any authority for such strategy being used.

ANYONE actually DONE any tests to see if there is greater advance with Premium than with Regular, and if so, how many degrees, and at what parameters, such as Load & RPM?

ANYONE know of any way to be able to read knock sensor signal in real time (Status/Live Data) or of any fault saved in memory if it detected knock, so we could determine if the timing is being retarded or knock is being detected?

George

[tlow98]

Originally Posted by Psyphertext

So I ran a tank of 87 through over the past week due to getting yelled at for my fuel budget. Yikes! My fuel mileage crashed and I could tell the car didn't have the scoot it had on 91. Just because you can doesn't mean you should when it comes to fuel. As noted by others, premium car, run premium through it. Remember that if you use the fuel economy needle to guesstimate, chances are you will be off 10-20 mpg versus the digital. I run off the trip meter and this change was significant on 87 octane...As in a 40 mile loss in economy across three quarters of a tank with no out of pattern driving across 2 weeks. 09 328i with 68K on the clock, no mods. 91 got put back in this morning, so if this pattern works, it should go back up. I also buy fuel in the morning to maximize the density since fuel expands in heat and contracts in the cool.

A well known tip: If you know where your local gas station delivery trucks are getting their fuel from, you will find that many get it from the very same supply point...more often than not. That should tell you that if the supply point is the same that the only difference is the in-ground storage tanks and the pumps. Storage tanks take on water a bit too easily in the U.S. and sometimes you can tell when condensation is in the system.

Run 89 if you need cheaper fuel in the moment or tough it out with 91. Avoid 87.

Weird. I have a 100 mile coming mute that I track to the mile and I have found no meaningful difference between 87 and 91. This could be due to our driving style, tho. If you drive the car much harder than I do then maybe you’re getting less from your gasoline volume.

And as far as performance we’re talking 2-3%. Even trained racing drivers have a hard time noticing 10%. You have one accurate butt dyno.