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10-11-2012, 01:09 AM | #1 |
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My reflection on 87 Octane (vs. 93)
So my brother thought he was being nice by putting gas in my car, but little did he know that I fill it up with 93... Anyway, I noticed some things here, and was just wondering if others in this situation noticed the same. This is regarding my N54 engine, although I assume the same experience would occur with the N55, could be wrong.
First, I am getting much better mileage! I'm just below a half a tank, with the amount of driving i've done, I should be below a quarter tank! This, apparently is the upside, in my personal experience. However, performance is compromised, as expected. The torque is just plain slower, and I notice much more lag. It is easily noticeable, since I drive always with 93 in the tank. IMO having the 93 is a must. If there are people out there not running 93 then you're not realizing the most potential of the car. ![]() |
10-11-2012, 01:17 AM | #2 |
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Kudos to your brother for putting gas in the tank!
I can't even imagine putting regular gas into a turbo motor. The engine controls will keep harm from being done (short term), so you could use it in a pinch. It does handcuff performance, though. Even my NA 128 is set up for premium gas. Inside the fuel filler door, it does say "91 octane recommended." I haven't used anything else. |
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10-11-2012, 06:48 AM | #3 |
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You are getting better mileage because the engine has retarded the timing to compensate for the lower octane. If u really want good gas try sometime mixing a gallon of e85 with regular 87 octane. I used to do this n my turbo a4 and the difference in performance from 91 or 93 was amazing. You have to be careful though because too much e85 will 1 harm your fuel components or 2 make the octane to high and the car will go in limp mode. Basically I would run my tank below a quarter left. Throw n 1 gallon on e85 and then fill up the rest with 87. E85s octane is an average of 106 so when mixed with regular it makes it about 96 or 97 which is like what they have in Europe and Japan and partly why their cars perform better.
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10-11-2012, 07:12 AM | #4 |
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If you get better gas mileage at the expense of performance, does that suggest that 87 would be good for a long road trip where power isn't a concern? My fuel door says "minimum 89 octane"... so I can't imagine that I'd be damaging my engine if I used that.
On the other hand, if I'm using the "fuel economy" mode on my JB4 tune, the timing is probably already adjusted without needing to change the fuel grade...
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10-11-2012, 10:05 AM | #6 |
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10-11-2012, 12:25 PM | #7 |
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Premium fuel gets better gas milage because the higher octane allows the engine to advance timing because it doesn't see knock as early. This inproves the efficiency of the engine and equates for slightly better gas milage as a result, tho it is not much, maybe 1 mpg if that. Likely the OP is just seeing a random sample that is higher than his average.
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10-11-2012, 12:44 PM | #8 | |
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^It's not misinformation. I'm not telling you that you'll get better mileage. I'm simply telling you that this is what I experienced. I've been pushing the engine harder, to try to get rid of this gasoline, lol, and it won't disappear like it usually does. |
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10-11-2012, 02:27 PM | #9 |
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10-11-2012, 04:21 PM | #10 | |
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10-11-2012, 05:17 PM | #11 | |
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Waiting on that LCI M240i...
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10-11-2012, 05:42 PM | #12 | |
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In regards to whether or not better fuel consumption is realized with lower octane, it seems like there's too many variables to fully come to a conclusion. It just seems that from my experience with it, I've made a conscious effort to consume more of this 87 octane, yet I still notice an obvious difference in how much gas I have left. In any case, I'm just surprised that there's no research that's been conducted to come to a conclusion on this (if there is, excuse me, b/c I haven't came across it yet.) |
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10-11-2012, 06:28 PM | #13 |
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Its a pretty well known fact, theres been load of research over the years. Nothing recent however because it is considered a law of automotive science.
And pushing your car harder on 87 octane to use up gas is a very unwise decision when your car requires premium. |
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10-11-2012, 07:19 PM | #14 | |
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For example: if an engine run with 87 octane makes 100 hp at 50% throttle, firing 10 degrees before top dead center. And that same engine run on 93 octane makes 105 horsepower at 50% throttle, firing 5 degrees before top dead center. Then you could reduce the throttle of the engine when run on 93 octane to 45% and make 100 horsepower and save some gas, while getting the same amount of power as the 87 octane. |
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10-11-2012, 08:57 PM | #15 | ||
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I just learned something new. Thanks man. While I know a decent amount I don't know everything.
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10-11-2012, 09:22 PM | #16 |
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Lots of misinformation here... I think Stohlen might be the only person that knows what he's talking about. No offense to anyone, just a warning to not believe everything you see posted on the internet.
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10-12-2012, 12:01 AM | #17 | |
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My old E36 with the M42 engine had multiple knock sensors connected to the engine block... Just wondering.
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