I messed up, what now.

[deportes]

Gassed up the 92 500SL and inadvertently pressed the 89 octane button instaed of the 91 octane. Filled the tank, Car idles a little rougher.
Will it cause damage to the engine?
Don't really want to remove and replace. Gasoline is not something I like to play with.
Should I buy a octane booster or just wait till I use up 1/2 the tank and refill with higher grade.

[stats007]

MB advise against using octane boosters though mainly with modern engines. I can't see there will be a problem - drive it sensibly (rpm below 4000) and just fill up with high octane. Lower RON just means the timing will be adjusted and there's the chance of pre-detonation. One tankfull won't hurt.

[Strife]

This may be true for cars with knock sensors, but for cars without (meaning, the timing will not adjust for pinging) like 107's, it would be a good idea to put octane booster in the car if any (any) knocking is heard.

[page62]

Try not to accelerate hard until you can get some 91 in there. This will help reduce pinging.

However, I imagine the R129 has a knock sensor. I'd be surprised if it didn't!

[Kebowers]

the car does have knock sensors that will retard the ignition timing to try and prevent knock. Drive it moderately--no foot on the floor, long up grades at high speed, towing, etc and it should be just fine--with a little less power.

Fuel economy will suffer at highway speeds and moderate loads though.

[iwrock]

Baby it a bit, and just don't worry about it. We did it in the 600, and it was fine. You can feel the difference in power though. I would reccomend driving it to get the fuel out, then from now on, just run the 91 or higher.

[bhatt]

Just drive like a grandma until you burn 1/2 tank (slow acceleration, don't hit the gas hard, etc.)

Once down to 1/2 tank, fill with 91 octane. The mix of 89+91 will give you approx 90 octane which isn't too bad. After burning another 1/2 tank and refilling, you'll be up to 90 1/2 which is close enough to resume normal driving!

Neal