Mattsuzie,
What they mean be PREMIUM is a minimum octane rating of 91.

Steveblf,
Great info! You're so clever.

Any words of wisdom out there on the old trick of adding not more than 2 moth balls (naptha) to a tank of gas to raise the octane rating by a couple of points? I've never tried it, but I'm told that it works and have always been curious.

Correct me if I am wrong, but all US pre 1986 cars require no more than 87 octane fuel. All newer models except for the 1986 190 2.3 require 91 octane. If your car runs bad on 91 octane, something is wrong. I would suspect an incorrect timing problem if all "wear" items are fresh.

Ron,
To answer your question,I know a guy who put 2
mothballs to his gas believing it will raise octane rating,guess what happen? It clogged up his fuel
system.Some say it has to be disolved before
adding it to your gas.Never tried it.Never will.
Clauser1

I filled up with 89 octane one time
 

and was so nervous about "flooring" it that I will never put anything less than 91 in it again (the E320). This weekend while in the Commerce, Ga area I found some 105 octane "racing fuel" sold at a gas station right off of I-85. It was $3.99/gallon but I'll bet it was some good stuff.
Jim
'85 300D
'95 E320
'97 CRV

Living in the midwest, the highest octane I can find locally is 92.5, but it contains ethanol. I have been told to avoid gas with ethanol as your engine "reads" it as octane thus negatively effecting performance.

What are your opinions of gases containing ethanol?

Brian,
I posted a thread about ethanol& methanol not too long
ago,and I never got any response so,I ask a dealer about it.
They said that we can run fuel w/10%ethanol or 3%methanol
but cannot be mix together.They are not compatible.In that
case I stayed w/Shell which contains no more than 10%
ethanol.My car likes Shell the best anyway.

Clauser1

Thank you Clauser1, I may try running the 92.5 with ethanol for a tank or two.

One more question, you know of any good MB tuners in the Chicago area? Someone with turbo or supercharger experience? I ran across one webpage, but damned if I can find it now!

Thank you!

Brian,
There are so many good MB mech.in Chicago area.
But most of them are very expensive.The one who I trust
my car with,is European Am.Motors.Located at Lincoln&
Addison.3541N.Lincoln Ave.Chicago,Ill.60657
Ph.(773)929 4288 or 9293764.Ask for Rudy an Austrian guy
whose very knowledgeable in MB(his specialty),and the owner
of the facility.See if he can help you.
Good luck!
Clauser1