12-13-2011, 09:41 AM | #1 |
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Fuel Type
So, while waiting for my X3 I am reading the owners manual. I had originally intended and believed that the car required high octane (91+). Reading the manual suggests 91 or even 89. Oddly, it doesn't say 91 or higher.
So what do you guys recommend and use? When you pull up to the stations with 94 do you use it or stick with 91 (around me, many Sunoco's have 87, 89, 91 and 94)? I also know that octane does not equal performance but the combustion needed for the engine to operate properly. I got the 28i by the way. |
12-13-2011, 09:51 AM | #2 |
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I always go with the highest octane available - even if high octane is not required, it is suggested and the car will lose some performance with lower octane gas....I have the turbo though and always will go for 91+ octane.
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12-13-2011, 09:53 AM | #3 | |
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12-13-2011, 09:54 AM | #4 |
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I have the Turbo as well so I stick with 91 or higher.
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12-13-2011, 09:58 AM | #5 |
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I have an X3 28i. When I filled up the gas tank today (for the first time!) I noticed the label inside said to use a minimum of 89 octane gas. Do I really need 93, or is 89 adequate?
It seems to me that this should be a binary decision - either the gasoline is high enough to prevent premature combustion, or it's too low and the anti-knock mechanism will need to kick in. Performance should not improve gradually. Am I wrong here? PB2 |
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12-13-2011, 10:02 AM | #6 |
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Got to agree PB. The knock sensor will just retard timing and in turn reduce performance.
BTW, how do any of us know what is below the pump nozzle? For all we know it's one tank feeding three different pumps. |
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12-13-2011, 10:28 AM | #8 | |
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This always reminds me of when a Turkey Hill opened up near my parents in PA. For opening weekend (years ago) they offered all three grades at $1.00 a gallon. Everyone was in line for 91 octane. I loved seeing the guys with the 89 Chevy filling up with 91. |
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12-13-2011, 10:36 AM | #9 |
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So I'm still confused - should I put 89 or 93 in my BMW X3 2.8?
The manual recommends AKI 89 or 91. Then it says: The minimum AKI is 89. If you use gasoline with this minimum AKI rating, the engine may produce knocking sounds when starting at high outside temperatures. This has no effect on engine life. Minimum fuel grade. Do not use any gasoline below the minimum specified fuel grade; otherwise engine damage may occur. |
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12-13-2011, 11:25 AM | #10 |
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Have 35i - I always use 91 but could use 94 as well. Doubt the 94 would make for improved anything, except more dollars to Chevron et al.
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12-13-2011, 12:35 PM | #12 |
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Just use the highest grade you can find.
The difference between the lowest grade and highest is less than $5 each fill up (at least where I live), so the way I see it is if it doesn't do any harm why not use the highest grade since using a lower octane could potentially be bad for the engine. |
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12-13-2011, 01:33 PM | #13 | |
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12-13-2011, 08:00 PM | #14 |
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I have the X3 28i. For what it is worth I rotate the 89 to 91+ octane. I usely don't let my gas tank get below a 1/2 tank. So one time I will fill it up with 89 then the next time 91 to 93. So you have the happy medium and I don't have any issues runs great.
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12-13-2011, 09:51 PM | #16 | |||||
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I would argue that the naturally aspirated BMW engines don't require the high octane fuel they call out. But I wouldn't actually argue not putting in the recommended fuel unless you feel comfortable with the risks. |
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12-14-2011, 12:31 AM | #17 |
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Less octane will cost you torque and power, plus the engine might not run as smoothly and not as "lively". The higher your altitude, the more you'll feel it.
In Western Europe you fill up with 95/98, so the U.S. 91 is in no way luxurious. And there is no such thing as too high octane in retail fuel. With each ignition the ECU will fine tune the timing, and the better the fuel you feed him the better the engine will run. |
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12-14-2011, 01:13 AM | #18 | |
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12-14-2011, 02:47 AM | #19 | |
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The compression ratio of your engine is the ratio of the volume of the cylinder at bottom dead center to the volume of the air at top dead center. Your engine management cannot change the compression ratio to increase the compression ratio (and thus increase power). When you burn fuel that is too low of an octane rating your engine simply caps the maximum throttle position to reduce the manifold pressure and reduce the chances of detonation. You CANNOT improve fuel efficiency or power with a higher than required octane ratio. Formula 1 cars don't use a very high octane fuel (relatively speaking). This is because they are running at such high rev's the fuel cannot detonate (not enough activation time) even though the temperature is high enough. It does not affect their power output. |
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12-14-2011, 03:00 AM | #20 | |
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Last edited by Bimar; 12-14-2011 at 03:11 AM.. |
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12-14-2011, 03:04 AM | #21 | |
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Ignition timing of course influences engine output. And that's where the benefit of higher octance numbers come into play. And who has been talking about compression ratio?? |
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12-14-2011, 03:16 AM | #22 | ||
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The energy released by your gasoline can be very easily modeled with a simple thermodynamic process and a stoichiometric chemistry balance. In no way does the octane rating of the fuel affect either of these properties. Can you explain to me the properties that a higher octane rated fuel adds to the equation that allows it to generate more power? Quote:
Yes a car retards the ignition with fuel that is too low of an octane rating. But if you fuel has a sufficient octane rating that detonation does not occur than your timing is not retarded and further increasing octane is not beneficial. |
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