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      11-22-2012, 07:41 PM   #1
ndog14
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Octane, what to use

I spent 2 hours in a car today traveling so I had time to read the November issue of the Roundel and one piece stuck with me. It is Mike Miller's Tech Talk concerning regular and premium gasoline. The question is regular v premium blah blah blah, 2008 335 auto. But Mike Miller's response is great, I'll transcribe verbatim:

It never ceases to amaze me how many people will pay $50,000 for a BMW luxury sport sedan with a 300-horsepower turbo engine and then go out and buy the cheapest gas they can get. Anyway, we have to print out one of these low-octane-fuel letters every year, and yours is excellent. You are obviously a very bright young man, and your automotive knowledge is surprisingly good for what I like to call the Y-Me? Generation. Still, I can practically guarantee you that your uncle will think of you as a kid when you're 40. Suggestion: Never give automotive advice to family members. They never listen anyway.
Here's the deal: All of what you wrote is correct except for the increased emissions. The engine will detonate (ping) on the lower-octane fine, but the knock-sensing ignition system will detect detonation almost before it occurs (not quite, but almost), send that information to the ECU, and the ECU will retard ignition timing to eliminate the detonation. There are four things to bear in mind about this process:
1. First, retarding the ignition timing reduces engine power output. Practical result: The driver pushes the car harder. It is this part of the equation that causes the engine to use more fuel, not the lower-octane gasoline per se. To the extent that using more fuel increases emissions, you are right about that, too.
2. Second-and I hesitate to say this, because it throws people into a dither-I suspect that the ECU is retarding ignition timing even with 93-octane fuel. I'm not sure about the direct-injected cars, but the M54 engines definitely do this, because 93-octane fuel isn't enough for that engine. (It's also possible that what's being sold as a 93-octane does not always have a true 93-octane rating.) It's important to bear in mind that the ECU will only retard timing so much, and then you'll have detonation.
3. In the case of a turbocharged engine with a high compression ratio, if you actually get to the point where the ECU cannot retard timing any further, and the engine actually starts pinging, chances of engine destruction are greater than would be the case with a normally-aspirated engine.
4. American gasoline is usually contaminated with ethanol, and in most cases it has insufficient detergent additives. Ethanol does raise the octane rating a bit, but it has less energy than gasoline and makes less power. All but the top-tier gasolines (www.toptiergas.com) have insufficient detergency-and frankly, I have my doubts about top-tier gas as well. Moreover, gasoline refiners tend to put less detergent additives in their lower-octane fuels. The end result of this is carbon build-up in the intake valves, spark plugs, and the top of the pistons. Carbon build-up on the top of the pistons, can over time, artificially raise the compression ratio, which increase the incident of detonation (pinging). The carbon can also become hot enough to detonate the air-fuel mixture before the spark plug fires. This creates enormous stress of the engine.
In my opinion, the bit about running regular gasoline could have been edited out of Michael Bird's letter. "Ran fine" is subjective, and Mr. Bird was probably unaware of the unintended consequences. The spec fuel for the car is minimum 91-octane, preferably 93 or higher. You can run lower octane in exigent circumstances, such as when traveling in an area where high-octane fuel is not available, but not on a regular daily basis. Premium-fuel cost is not "spending unnecessary money," it is spending necessary money.
Finally, remind your uncle that his engine is due for new spark plugs at 45,000 miles. Frankly, I think every 30,000 is a better interval for the turbocharged engines.
I've sent you a number of BMW service-information bulletins regarding fuel, as well as the Lifetime Maintenance Schedule and the N54 engine-recall bulletins. Most important among the fuel bulletins is the one about using original BMW Fuel System Cleaner Plus every 3,000 to 5,000 miles. That mandate from BMW is the direct result of low detergency and ethanol contamination is U.S. gasoline.

For reading ease I did not bold, italized, underline, etc.
If I made a mistake concerning my transcriptions of Mike Miller's reply please post it so I can make the necessary edits.
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      11-22-2012, 07:46 PM   #2
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good read
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      11-22-2012, 07:57 PM   #3
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Most important among the fuel bulletins is the one about using original BMW Fuel System Cleaner Plus every 3,000 to 5,000 miles. That mandate from BMW is the direct result of low detergency and ethanol contamination is U.S. gasoline.

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Ive never heard of this before..... Anyone?
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      11-22-2012, 08:08 PM   #4
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Eric" all I know is that using cheap gas station resulted in clogged injectors and dirty valves. Its been a shock for me, I came from Europe and constantly used the lowest possible grade an price without issues. In the Us it seems you have to make an audit of gas stations to get something that will not destroy $1000 of engine parts in 50 miles

Ethanol is crap (for the reasons exposed in the op's thread, and more, it also eats through many gaskets and plastic tubings that should last forever but fail miserably because of it). I'm so furious it is mandatory in my state Ethanol is sso cheap that it is often dilluted at much more than 10%. Some random measurements have shown up to 25% ethanol, that is garanteed to make damages in cars that are not designed for this.

The car runs fine on lowest grade, if its the only thing available. It runs better on 91. 91 or 93 makes no practical difference. Brand makes a difference (top tier thing), but particular gas station makes more difference (in addition, I filled up in stations where I put more than 16 gallons in a 15 gallons tanks, yep, right... ).

End of rant
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      11-22-2012, 08:29 PM   #5
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Good read. Thanks for the post!
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      11-22-2012, 08:48 PM   #6
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I'm a V-Power guy myself. Anything else I should be doing to maximize my car's zoom factor?
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      11-22-2012, 09:47 PM   #7
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Quote:
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Eric" all I know is that using cheap gas station resulted in clogged injectors and dirty valves. Its been a shock for me, I came from Europe and constantly used the lowest possible grade an price without issues. In the Us it seems you have to make an audit of gas stations to get something that will not destroy $1000 of engine parts in 50 miles

Ethanol is crap (for the reasons exposed in the op's thread, and more, it also eats through many gaskets and plastic tubings that should last forever but fail miserably because of it). I'm so furious it is mandatory in my state Ethanol is sso cheap that it is often dilluted at much more than 10%. Some random measurements have shown up to 25% ethanol, that is garanteed to make damages in cars that are not designed for this.

The car runs fine on lowest grade, if its the only thing available. It runs better on 91. 91 or 93 makes no practical difference. Brand makes a difference (top tier thing), but particular gas station makes more difference (in addition, I filled up in stations where I put more than 16 gallons in a 15 gallons tanks, yep, right... ).

End of rant
The tank is 16 gallons, not 15. None of those are my words, Mike Miller's in Tech Talk in the Roundel. In west PA and northeast OH its 87, 89, and 93 except at Sunocos and the price difference between 91 and 93 is $.02 so I just go with 93 if I'm stuck with Sunoco.
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      11-22-2012, 09:48 PM   #8
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Ive never heard of this before..... Anyone?
I've seen it for sale at parts counter at the dealer.
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      11-22-2012, 09:51 PM   #9
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I'm a V-Power guy myself. Anything else I should be doing to maximize my car's zoom factor?
Same here, unless i get a giftcard for another station. Free 93 octane is the best kind

Otherwise, im always V-Power.

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I've seen it for sale at parts counter at the dealer.


Thanks, i guess i should take a look at this. Might be an extra step to prevent misfires???
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      11-23-2012, 09:37 AM   #10
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Quote:
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Same here, unless i get a giftcard for another station. Free 93 octane is the best kind

Otherwise, im always V-Power.





Thanks, i guess i should take a look at this. Might be an extra step to prevent misfires???
Interesting read from someone without a vested interest. Might try that fuel system cleaner. Thanks.
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      11-23-2012, 10:37 AM   #11
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Can anyone confirm if techron etc fuel cleaner actually works, or more importantly, helps or hurts? How about those of us with tunes?
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      11-23-2012, 11:12 AM   #12
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Can anyone confirm if techron etc fuel cleaner actually works, or more importantly, helps or hurts? How about those of us with tunes?
I'd try BMW. Why not?
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      11-23-2012, 11:19 AM   #13
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only use 93 for security despite the high prices
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      11-23-2012, 11:53 AM   #14
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only use 93 for security despite the high prices
+1. I run a light tune package (JB4 G5ISO/FMIC) designed for 93 octane & run 95/96 just in case. If you look at the engine logs its not all that uncommon for boost to spike & exceed the set targets at WOT.
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      11-23-2012, 12:00 PM   #15
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+1. I run a light tune package (JB4 G5ISO/FMIC) designed for 93 octane & run 95/96 just in case. If you look at the engine logs its not all that uncommon for boost to spike & exceed the set targets at WOT.
I've seen 108 in FL. Do they have 95/96 in NC?
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      11-23-2012, 12:34 PM   #16
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Quote:
Originally Posted by ndog14 View Post
The tank is 16 gallons, not 15. None of those are my words, Mike Miller's in Tech Talk in the Roundel. In west PA and northeast OH its 87, 89, and 93 except at Sunocos and the price difference between 91 and 93 is $.02 so I just go with 93 if I'm stuck with Sunoco.
I never fill more than 15.3--15.4 because its never really empty. Now there is that one gas station where it consistently fill in 16+ gallons.

Yeah, the 91 is hard to find and doesn't matter. I use 93 most of the time because that's what's available anyway.



The Techtron stuff works, its actually quite miraculous the difference it makes. It is suspected that BMW cleaner is actually repackaged Techtron, but the price difference is insignificant, so if you prefer OEM name go for it.
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      11-23-2012, 01:25 PM   #17
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Quote:
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I never fill more than 15.3--15.4 because its never really empty. Now there is that one gas station where it consistently fill in 16+ gallons.

Yeah, the 91 is hard to find and doesn't matter. I use 93 most of the time because that's what's available anyway.



The Techtron stuff works, its actually quite miraculous the difference it makes. It is suspected that BMW cleaner is actually repackaged Techtron, but the price difference is insignificant, so if you prefer OEM name go for it.
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      11-23-2012, 01:33 PM   #18
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Yeah but at 9000 miles how much of difference can Techron really make?
Not very much I imagine...
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      11-23-2012, 01:53 PM   #19
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I work at a Ford dealer and screwed up as I fill many cars a day. I filled mine from empty to the brim with 87. It was that moment you look down and just laugh as theres nothing you can do at that point. Luckily I burn up a tank of gas every 3 days. I have logged the car pulls timing as well on tune 5 its staying in 8psi boost range.
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      11-23-2012, 02:03 PM   #20
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Damn, the only top tier gas we have here is Mobil and they're disappearing/being replaced by Sunoco's.
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      11-23-2012, 02:05 PM   #21
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Quote:
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I've seen 108 in FL. Do they have 95/96 in NC?
No - its a 93/100 mix.
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      11-23-2012, 02:36 PM   #22
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only use 93 for security despite the high prices
Same here.
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