89 Octane?

[karamazov2]

Nearing my 600 mile service. I did notice, while filling up that BMW is suggesting 89 Octane. I may be mistaken, but I recall my '07 taking only premium (with anti-knock sensor for lower grades, when necessary.) I guess I'd have assumed the newer engine would be sporting higher compression ratios and call for premium. I've been topping off with 91 anyway, to avoid the 10% corn juice.

Does anyone have any insight on this?

[Catchina]

I think 89 is minimum, higher is better and should also produce more mpg.

[MTBeemer]

I remember a software update coming out a few years ago that made the engine better performing with lower octane fuels.

[ammolab]

The engine management system is capable of tuning ignition timing to produce maximum power on 91 to 93 Octane. Total power output will be lowered with lesser grades of fuel if the Knock sensors detect pre ignition (ping/knock). Such a signal from the knock sensor will result in a reduction of spark advance to protect the engine. MPG may be slightly altered as well, but only if your driving habits (Large throttle opening for acceleration/top speed) require frequent timing pulls by the ECU.

If you have a LONG INTERSTATE run with nothing much but High RPM cruise.... you may use 89 Octane and notice nothing at all. This constant mild throttle, high intake vacuum, high RPM running is a real low octane situation for any engine.

If you are blasting from curve to curve on a hilly mountain road...well now you need that 93 octane to prevent ping/knock or a serious ignition pull from the ECU. In this situation with 89 Octane you would notice a loss of peek power and also MPG from the frequent running with retarded timing.

[rokinrider]

Living in Iowa the ethanol state sometimes it's hard to find a fuel stop with no alcohol. We have premium with and without 10% in it. I do avoid it like an STD but some times ya got no choice. It seems to run fine I have not noticed any pinging but I try and avoid it. My trusty S-10 doesn't mind it????