My 318 ti Owner's Manual refers to AKI of 90. The AKI (anti-knock
index) is the same as the Road Octane Index which is also
known as the PON, or Pump Octane Number, both of which
are the average of the Mon (Motor Octane test) and the Ron
(Road Octane test). This is according to the following
website:
http://www.shell.ca/code/motoring/en...fo/jargon.html

This is what it says:
"RON, MON and Road Octane:

"RON stands for a fuel's Research Octane Number. This value is
measured under fairly easy test conditions. The MON, or Motor Octane
Number, is a tougher test measured at higher engine speed and
temperature. And the Road Octane Number - the octane number that
relates most closely to actual driving conditions - is the average of
these two values, i.e. Road Octane = (RON + MON)/2. The Road Octane
Number is more frequently referred to simply as the octane number.
Always be sure that the octane number a vendor advertises is its Road
Octane value, not its RON.

"Anti-Knock Index (AKI):

"The same as the Road Octane Number. It is a numerical description of
a fuel's ability to resist engine knocking. Anti-knock index is a more
accurate description than octane number, which is why in the U.S.
fuels are often given an anti-knock index instead of an octane
number."

So when my Owner's Manual calls for 90 AKI fuel, it is asking for
93 RON (+/-). Seems an 89 AKI would not involve much risk
at all and it would save 10% on fuel price versus 93 AKI (premium).
Any risks here other than loss of power and mileage? Not
worth wrecking the engine to save on fuel expense!

Fritz Wagner

On Wed, 23 Feb 2005 11:26:49 -0800, "Jeff Strickland"
> wrote:

>
>"The Malt Hound" <Malt_Hound@*no spam please*yahoo.com> wrote in message
...
>>
>> "Jeff Strickland" > wrote in message
>> ...
>> >I have been using the mid-grade for years.
>> >
>>
>> That is what is recomended for all 3 of my BMWS (E36M50, E34M60,
>> E36/7M52).
>> AKI 89 or better. It's in the owners manual and on the gas caps.
>>
>
>I don't know about the gas caps, it isn't printed on mine nor is it printed
>on the inside of the fuel door. The Owner's Manual does say that 91 (RON) is
>the preferred fuel, but 89 will work fine, that is what I use. I have never
>tried 87.
>
>
>
>
>

Columbus, Ohio