Whats the difference if you put in 89(special) vs 91(super)? is it MANDATORY that you put in 91 or is it ok with 89? Are there gonna be long term effects on the engine, such as abnormal wear, power loss, etc? Thanks guys.

 

u need 91. OEM gas. the higher the number the more combustion. Well i know that the inline 6's need it. not sure about your 220. Whats it say in the manual.

 

In my C230K owners amn it states 93 octain. It also says that if you have to put the lower octains then only use a 1/4 tank or enough toget to a station that has 93 then fill the tank. It strongly recomends the highest octain.

 

GDawg I've got a 94 c220 too, my manual says our cars need 91 octane %. This number is related to the compression ratio in our engines I believe. Using lower-than-recommended octane gasoline is supposed to lead to the gas blowing up prematurely when compressed in the cylinder, as opposed to when the spark plug sparks. This is also called "Knocking" and isn't a good thing. But I've read that our cars have anti-knocking sensors in them that do something (like change ignition timing?) to prevent knocking from happening. So my guess would be that using 89 octane wouldn't noticably affect anything in the short term at least. Maybe decreased performance if the anti-knocking sensors kicked in.

Oh and I've read posts on other forums from mercedes drivers that use lower octane gas without problems. I don't remember where I saw this tho

 

I saw a 99 S430 towed into the dealer last week because the lady who owned it always put in 87 octane. The dealer voided the warranty on the car and she had to get an engine rebuild. Is it really worth a couple of bucks every two or so weeks to back down on octane? I'm not trying to make it sound like a status symbol or anything but if you can afford a Benz you can afford the gas.

 

One of my friends has a ML430 and he has been putting in 89 Octane (Plus in MA) since he got the car...good so far, been 4 years already. So i was just wondering.

 

if your manual says use 93 you best use 93. if you cant get 93 get the highest possible.

 

I've seen some towns here in Texas that only carry 90 as the highest. Me, personally, I've used nothing less than 89 in ANY of my cars. I used premium in my MAXIMA, middle grade in my YUKON, and I use nothing but premium in the Benz. The hightes I've seen available here in Midland is 92, maybe I saw 93 once somwhere, but for the most part all stations here carry 91 as the highest octane. I will share this little tid bit, though. I used 87 once in my Maxima after running only premium for all of the car's life and the damn thing kept dying on me. I never used 87 in anythng again after that.

 

Everything in Alabama is 93 with the rare occasion of some old country station that still has 92. Our Amoco stations are 93.5 octane.