My parents borrowed the car and mistakenly put 89 octane instead of 93 not knowing I drove the car and it died yesterday and won't start so now it's at Benz and don't know to much about this vehicle have not even a week. According to many articles this should make the car run sluggish and that I should just get 93 an a can of redline octane and should clear it up no problem any suggestions?? I'm completely sick about this

Ok, I'm no Mercedes God however I have firsthand experience with putting 89 in my 2004 S600 V12 and didn't have any problem whatsoever. Unless the vehicle was subjected to some extremely harsh driving conditions the most you should have experienced is a bit of sluggishness as you have said. Most people don't have a clue as to why their car says to only use premium fuel. It has everything to do with how the engine is designed. For example, let’s take a typical family sedan with a standard V6 with a compression ratio in the 8 to 9 range that runs fine on 89 octane and produces 220 hp. Most people think that if you put in 93 octane fuel this same car will have more power and better fuel economy. That is not true and actually may have lower power and worse fuel economy. The reason for this is the higher octane fuel actually has less energy than 89 octane fuel. Yes, you heard me correct. So you may wonder, “why do we have higher octane fuels?” The reason is for those engines designed to run at higher compression pressures. It’s no secret that the more air/fuel you can get into the cylinder and the more tightly you can pack that air/fuel during combustion equals more horse power. However more pressure equals more heat, more heat means the fuel may pre-detonate. This pre-detonation is what is known as engine knock and under severe conditions can damage your engine. So higher octane fuels are formulated to resist pre-detonation thus the air/fuel gets into the cylinder for the combustion cycle. Now to get back to your situation. Under almost every conceivable “normal” driving condition your vehicle can easily adjust to lower octane fuel. Every modern engine, including ours has knock sensors. When the car senses pre-detonation condition by monitoring the knock sensors, it will back off the spark timing and/or increase the amount of fuel to cool down the intake tract thus stopping the pre-detonation condition. This happens very quickly. This is why I highly doubt that the single instance of putting 89 octane fuel into your car could possibly be the reason for the engine to die. Unless of course there were other mitigating factors such as extremely hot temperatures, very high sustained rpm, and possible other engine cooling problems or malfunctioning knock sensors.

Regardless I hope you get it fixed.

Take care,

Brian

Wrong gas would be filling it with diesel. Its just a lower octane and shouldn't effect the car running.

Right, 89 is fine. Perhaps you accidentally ran that 80% ethanol stuff, or worse...diesel. Either way, the engine shouldn't be siezed, but they'll probably have to clean out your fuel lines, drain the gas tank, clean fuel injectors.

Sitting here waiting from Benz to call it's like bamboo under the finger nails thank you for your imput based on your input and some good old research I'm leaning towards its not the gas situation and Mercedes also said that it wouldn't shut the car down .

It sounds like diesel to me, but the nozzle is typically a larger size on a diesel pump and wont go into your tank...just pull the gas cap and smell it.
If they put 89 fuel in it it is probably a bad coincidence to some other problem that would happen anyway...is the car in park and does it turn over at all?
Mike

I read through all of the threads again and there is a good point...if e-85 was put in who knows if it will run...it should still run, albeit poorly. Now you can at least tell them they cant borrow the car again...haha.
Mike

Hey
Just wanted to thank everyone for taking my stress level down about the situation, I am confident that the 89 octane is not the cause of the symtoms the car will be first in line tmrw for diagnostics so will know exaclty why she acting that way. Hoping its something real simple that is an easy fix. Thanks again for the advise and lessons learned one never let the parents borrow it again and lesson for them don't try and save 40 cents a gallon foe gas when driving $100.k car LOL serious will keep everyone posted.

Hey
Whats up, I got the beast back today, it was the crank shaft sensor, the gas tested fine and had the ABC flush bled and new fluid so she is ready to rip. Thanks again for all the feed back in that stressful moment.