I went and looked at a 2007 SL55 AMG with 46k miles on it on Friday.

My major concern is that even after it warmed up, there was slight shake in the motor at idle. I could put my hands on either side of the motor cover and could feel it knock.

The guy selling it said he had put 93 octane from a no-name gas station in it and was going to put shell v-power in it when it got low on gas.

Has anyone experienced the engine retarding timing when putting "off brand" gas in it?

Is there anything else I should look at before buying this car?

Other than the knock it seems like an amazing machine.

could be motor mounts and the transmission mount. very common and not a big deal. I would absolutely have a PPI done.

you have to take the car to mercedes and have a complete cpo inspection done, the car could cost thousands to fix if it has a small problem

I'm with the guys above. You might ask the seller when the last time motor mounts and the tranny mount was changed. I am on my 4th set of motor and and second set of tranny mounts. Mileage is at about 90k. No doubt my mods have made it worse, but these liquid filled motor mounts definitely wear out quickly.

I can't imagine the ECU pulling timing at idle because of off brand 93 octane.

BS, have an inspection done.

Take your time when purchasing any car. Do your research and have the car inspected by an independent mechanic who is familiar with that particular type of car.

It's probably normal noise for that car/engine. They are noisy due to the chain drive from the oil pump slapping the inside of the front timing cover when the tensioner spring loses some of its snap. It's more of a nuisance noise than anything.

Take the car to an MBZ dealership, have the pre purchase inspection done, have the service history pulled, have them give yo a budget to repair whatever they find. Then armed with all of that info make a decision. This process has saved me literally thousands of dollars and eliminated several very well polished turds over the years. Good luck.

I would add that you could post the list here for further discussion. There might be some items that have not been repaired that will likely fail. For instance the intercooler pump and the crankshaft positioning sensor.

I will definitely have them check it out, I just want to be there when they do it. I've had a lot of bad experiences with dealers and want to look at it myself.

I wasn't aware that the mounts went bad that quickly in these cars. Normally you can tell when a mount has gone by how it shifts or you can hear something knocking on acceleration or decel.

I just wanted to get some actual information from people who drive these cars and their experiences. I didn't know how sensitive the motor/ ECU was to what gas was in it.

Will MBZ tell me if the knock sensors are affecting the timing.

Full disclosure, I might have had one set changed out when it really wasn't necessary. Also, the mods put just south of 500 hp at the wheels and wheel torque is like 539. Lots of twisting going on when I light the little SL up.

I also used to visit the drag strip on a regular basis too.

I figured that had something to do with it.

I have over 80,000 miles on my SL55 and only recently had my motor mounts replaced. Essentially, the new ones eliminate vibration, and there is a noticeable driving difference from a smootheness standpoint.