I use the 91 Octane in my 04 Supercharged because thats what the Manual called for.

I have used 87 Octane at times, and really have not noticed any adverse effects, but I don't use the lower grade on a regular basis. Usually a few tanks when on a long trip.

 

Supercharged engines do require premium.

 

my 04 SCMCSS runs like garbage on anything else then 93. i mean no power, milage drops off at least 3mpg.

 

will running premium in a 3400 or 3800 nonSC make any difference??

 

Manufacturers say it's a waste of money. If your car don't require it then don't use it.

 

89 is the cheap stuff in iowa, and thats what it gets. doesnt seem to complain though.

 

91 all the way, my car runs way better with it over 89

 

I've been running 87 octane for 77,500 miles now and my computer says I'm getting an average of 24.8 mpg.
Recognize probably 75% of those miles are highway (I bought the car for long trips) so I suspect the
city numbers are lower.

 

No, it is just a waste of money. Premium does not burn any "cleaner" than 87. Higher octane is only needed when the compression ratio is higher (as with a supercharged motor) because it resists detonation longer.

 

I use regular fuel in my 04 Monte SS... I have noticed that you all say you get about 24-25 MPG - Anyone see 27MPH like I do...

I have reset it and all that to confirm it and computer says 27.2 - 27.5 MPG and thats constant driving at 70 MPH most times.

POST YOUR MPG's!!!