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1984 500sel
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35 Posts
Discussion Starter #1
I've only been driving the car a day now and just filled it up with cheap stuff. I was at a light and it would knock every 4 or 5 seconds. I know the motor mounts are about half gone and they told me it would shake a little when stopped. Is this the cheap gas, motor mounts, or some other gremlin? should I be putting prem in or is the cheap stuff good? thanks
 

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Moderator
1991 500SEC 55K mi. 1987 560SEC Now 153K mi. 2020
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5,177 Posts
Hi benz w126,

I don't think inexpensive gasoline will cause a knock at idle. It can do so on acceleration and under load however. The octane rating on the pump is the key pretty much.

If your manual says use XX octane fuel, I wouldn't personally go below that figure, just to save a small amount at the pump.

Another thought: The octane needs of the engine were determined for a new engine. What I'm getting at is an engine without ANY deposits on the piston tops, valve heads, or combustion chamber.

Wouldn't it follow that the engine with some miles (build-up) conceivably be more apt to need the benefits of the premium fuel?

2 cents, MBL
 

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1984 500sel
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35 Posts
Discussion Starter #3
I was just hoping this wasn't a timing chain issue. I dont mind putting the expensive stuff in however, if it doesnt need why bother. I also had a low opinion of the car but im starting to see past the dirt and grime and realizing how good of shape its in mechanically. now if I can just get the front windows down [8D]. This is the first v8 I've had and I love to hear rumble.
 

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W210, W211, W163
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274 Posts
I am having the same problem. Have you figured out what the problem is? I would appriciate it if you can let me know. Thank you.
 
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