Fuel mileage 87 octane vs. 93 octane
04-12-2007, 06:13 AM
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My Ride: 2005 e60 Titanium grey Auburn premium Sport 6-speed Logic-7 folding rear seats with ski bag Bi-xenon Cold weather package
I always use 93 octaone feul but this week my local station was out so I filled up with 87. I don't know if it is my imagination but I seem to be using more fuel than usual. I diden't reset my gauge, so I am wondering if anyone has tested the mileage with different octanes and if so, is there a drop in fuel mileage?
04-12-2007, 06:16 AM
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You will surely lose some horsepower. On a show a while back they ran a Porsche 911 on a dyno with lower octane gas and it lost a good bit.
04-12-2007, 06:27 AM
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My Ride: 2005 e60 Titanium grey Auburn premium Sport 6-speed Logic-7 folding rear seats with ski bag Bi-xenon Cold weather package
I'm not talking about HP, just fuel mileage.
04-12-2007, 06:31 AM
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It would take some fine testing to see the difference. I would suggest resetting your avg mpg for each tank and attempting to drive the same way for each one. Two or three rounds of each should do the trick.
But are you saying that you are more interested in mpg than bhp???!!!
But are you saying that you are more interested in mpg than bhp???!!!
04-12-2007, 06:38 AM
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My Ride: 2005 e60 Titanium grey Auburn premium Sport 6-speed Logic-7 folding rear seats with ski bag Bi-xenon Cold weather package
I could test it as you say, but that woud require me using 87 for a few more tanks, and that is a no-go as I am more interested in BHP than mileage 
, I am just curius if anyone has sussed this out.
, I am just curius if anyone has sussed this out.
04-12-2007, 06:49 AM
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Whew!! Thought you had lost it there for a minute. I would venture to say that use of any degraded fuel would have an effect on all performance parameters over the long run. Suffice it to say, our engines thrive on the best!
04-12-2007, 07:04 AM
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My Ride: 530d Sport Touring (E61). Silver Grey, Automatic, Professional SatNav, Black Leather, Heated Seats, Folding Mirrors, 6CD changer, Bi-Xenons, Bluetooth
When I had a 330Ci I changed from 95 to 99 octane fuel and noticed an almost immediate improvement in engine responsiveness, perceived acceleration and almost as importantly, in miles per gallon. I guess the better octane rating means the engine is operating much more efficiently.
On the downside, now that I have a diesel I haven't found that changing from 'ordinary' to 'premium' or 'ultimate' branded diesel makes any difference whatsoever in mpg or performance (unlike my ECU remap!).
On the downside, now that I have a diesel I haven't found that changing from 'ordinary' to 'premium' or 'ultimate' branded diesel makes any difference whatsoever in mpg or performance (unlike my ECU remap!).
04-12-2007, 08:20 AM
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My Ride: 2008 550, Carbon Black Metallic, Natural Brown Dakota Leather, Sport Package, Sport Automatic Transmission, Cold Weather Package, Power Rear and Manual Side Sun Shades, etc.
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Based on the science / technology (as I understand it, which is at an admittedly low level), I would think there would be a decrease in MPG. The engine will sense the lower octane fuel and adjust the timing accordingly so as to prevent knocking casued by the fuel spontaneously igniting before the spark fires. That means the spark will fire sooner, and over a fixed period of time, more often than if you used the recommended octane. It seems to me that this would burn through more fuel. Or, I could be all wrong.
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