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  • avatar subearu 08/15/08 11:33 pm PST

    91-93 octane is generally referred to as Premium or Super.

    Many sport sedans and other sporty vehicles recommend or require premium to obtain the hp ratings they have, not to mention the compression ratios, etc. However, since they've been tuned/programmed that way, feeding them something other than higher octane fuels will lead to the computer dialing back the timing to adjust for the increase knock that the lower octanes will make on these type of motors. Certainly, the computer can adjust somewhat depending on what the knock sensor feeds back, but there is a limit. Some motors can adjust enough to run on lower octane, others just simply can't. That knock or ping is never good on the motor. It can lead to carbon buildup and hot spots on the motor. Plus, when the computer dials back the timing to adjust as much as it can/needs to, your hp goes down, which also could negatively affect MPG a tad. So, you have to ask is there a benefit with all of this risk?

    You might be able to try midgrade or 89 octane and get by. But, you should try out a couple tanks to compare results. However, if you're buying a BMW, you should feed it premium.

    -Brian

Answers

  • bandit10 08/15/08 11:11 pm PST

    93 Octane would be the highest in your area. I would stay with it because BMW has your computer configured to take the higher. For performance purposes. If you choose to use a lower Octane you'd feel the lack of performance and proberbly ignition knocking. You don't want that.

  • subearu 08/15/08 11:33 pm PST

    91-93 octane is generally referred to as Premium or Super.

    Many sport sedans and other sporty vehicles recommend or require premium to obtain the hp ratings they have, not to mention the compression ratios, etc. However, since they've been tuned/programmed that way, feeding them something other than higher octane fuels will lead to the computer dialing back the timing to adjust for the increase knock that the lower octanes will make on these type of motors. Certainly, the computer can adjust somewhat depending on what the knock sensor feeds back, but there is a limit. Some motors can adjust enough to run on lower octane, others just simply can't. That knock or ping is never good on the motor. It can lead to carbon buildup and hot spots on the motor. Plus, when the computer dials back the timing to adjust as much as it can/needs to, your hp goes down, which also could negatively affect MPG a tad. So, you have to ask is there a benefit with all of this risk?

    You might be able to try midgrade or 89 octane and get by. But, you should try out a couple tanks to compare results. However, if you're buying a BMW, you should feed it premium.

    -Brian

  • tony78 08/16/08 1:05 am PST

    You know how they call bmw " The Ultimate Driving machine " ?

    Ultimate is german for,,premium fuel only.

  • karjunkie 08/16/08 8:38 am PST

    I own a BMW 5 series and can tell you that your car will work perfectly well on mid-grade 89 octane gas. In a pinch, it will run on regular 87 octane without any knock. The reason is that the sophisticated engine management computer on BMWs will reset the ignition to prevent knocking. If you want 100% performance from your engine, then you do need 93 octane, but in 95% of driving conditions, 89 octane will do.In fact, most BMWs' gas caps identify 89 octane as the reccommended fuel. Hope that helps!

  • MrShift@Edmunds 03/17/09 1:44 pm PST

    Generally when the automaker says "premium" they mean 91 octane or better.

    Your BMW will run on lower octane, but it will be slower and may get fewer MPGs. You cant' harm the engine (the computer will compensate for the lower octane fuel) but your car's engine will definitely let you know that it's not feeling as peppy.

    BMW uses premium because their engines are built to utilize the "even-burning" nature of the flame front created by higher octane fuels. You get a smoother, more powerful combustion.

    There is no more "power" in high octane fuel, just much better burn characteristics.

    American automakers often done require it because their engines are not built to use it.

    BMW wants maximum performance and engineers for it.

    Premium fuel is utterly wasted in an engine not built to use it, despite what people think.


  • bushwhacker1 07/05/09 4:56 pm PST

    From my first 318 Ti, to the 328 is, I did the test of using lower Octan rating for you. Yes you will save few bucks on your gas take and you will still think .. HAhahahah Suckers
    but you will experience at first some loss on powerage at the begining. you will tell me well so what I still get 5 bucks less on my gas and multiply by .. BLABLABLA
    Well at the end you will be the sucker at the auto repair and you will pay more than the few bucks you saved. I did it in 98-99 with a 323 I and the computer got messed up and trust me is not cover by the warenty of your lease.
    I you are that cheap to save few bucks on a gas tank get a Toyota or a Ford Flex-fuel, but do not get a BMW

  • alfred14 04/18/12 2:42 pm PST

    I've been arguing this point for years. Some insist that new cars make octane ratings obsolete, but regardless of the science behind what octane is all about, I've noticed that my own experience, even with a new 88 BMW 325is, and several other cars, higher octane yields higher mpg. Those who have tested this theory themselves, as I've read in several websites, agree strongly that more octane works better as long as your car can stand it. My opinion is that premium gas is actually marginally less expensive than low test, because the increase in mpg outweighs the slight increase in cost per gallon. The compensation done in cheaper cars for cheaper gas is only to prevent damage to the engine, the loss of power is not compensated. This is according to my own experience, and what I've gleaned from other sites.

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