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General Discussions about the 300M

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 #332720  by ks4ua
 May 30th, 2014, 11:12 am
LUNAT1C wrote:I stick to Shell 89. 91 has zero positive effect.
I think I will try a tank of that Shell 89 and see how it goes.
 #332727  by otto95
 May 30th, 2014, 12:59 pm
From the 2004 owners manual:

FUEL REQUIREMENTS

300M

Your engine is designed to meet all emissions regulations
and provide satisfactory fuel economy and performance
when using high quality unleaded gasoline having an
octane range of 87 to 89 or higher. The manufacturer
recommends the use of 89 octane for optimum performance.

300M Special Only

Your engine is designed to meet all emissions regulations
and provide satisfactory fuel economy and performance
when using high quality unleaded gasoline having an
octane range of 87 to 91. The manufacturer recommends
the use of 91 octane premium gasoline for optimum
performance.

I'll bet you notice a difference after a couple fill-ups, especially with the a/c on...
 #332735  by JTROANOKE
 May 30th, 2014, 4:55 pm
The 10% alcohol would have negligible effect on mileage, if they actually blended it with 87 octane regular. Unfortunately they blend it with 85/6 octane and count on the alcohol to bring the octane rating to 87. To some degree a higher octane fuel should theoretically give better mileage, because the knock sensor would allow slightly more advanced ignition timing. I would imagine if the knock sensor wasn't effective, our cars with their relatively high compression ratio would ping like crazy on regular. I have always run 87 in my car and have never heard audible spark knock, even living in a relatively hilly area like I do. I have tried 89 and the improvement in mileage was so slight that it was a wash against the extra price.
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 #332771  by adu1982
 May 31st, 2014, 12:42 pm
Same experience here, even highway wise, so i stick with cheap 87....