2000 S430 I drive
Do you notice a difference using anything but 93 grade ?
would it hurt the performance using anything less ??

 

91 works fine

 

This car "requires" fuel that has an octane rating of 91 or above.
There is an "anti-knock sensor" installed in your car, it prevents the engine from knocking if you put in fuel that is below 91.

 

Based on experience with the X5, I tried 89 in the S430 and I see no difference in MPG or performance from 93 just as in the X5. It is nearly impossible to find 91 here, It's 87,89, or 93. An occasional station has 91 and I begin to wonder if you are really getting what they claim, kinda like Decaf vs regular, do you really know? Local news has run stories on octane and coffee and found discrepencies not infrequently.

 

I do know the octane rating refers to molecule balance in the gasoline...so 91 means 91% of the molecules are equally balanced and separated and 9% has irregular molecules...Higher octanes cause more controlled explosions to move your pistons....I have a 94' s420 been using "87" since I got the car 6 months ago..Common sense tells me I can't do any damage with a lower octane, and actually could mix octanes if I wanted to...Can anyone prove me wrong??? BTW, seen a gas station here claiming a 100 octane gas, they call it racing fuel....

 

[sm=oopssign.gif] Disregard my previous post, I got that octane calculation from some tv car show...That guy obviously didn't know what he was talking about....sorry....Using low grade gas and mixing was my opinoin. My company gave me a gas card I thought filling a 26 gallon tank with premium would be pushing it....But you know what, I bought a mercedes, so if they don't like it they can f*ck off..

 

You can mix 87-Octane regular Fuel and 93-Octane regular fuel. It's ok. I worked for a gas station back in high school. The delivery truck mixes 87 and 91 in a certain ratio to fill the reservoir of 89-Octane.

(It is a different story when E85 or 89-Octane fuel with 10% Corn Ethanol are involved. No mixing! )

100 Octane is not real race car fuel. It is called 100LL, used in propeller planes.

Race cars use 110 Octane.

Putting 87-octane fuel in Premium-Gas-Only car may not create knocking due to the thoughtful ECU programming. But, in the long run, the valves are gonna go. If the car has super-charger, the valves will die very fast. Then super-charger will give in too.

 

good point, i agree with the post above