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1988 300 SE
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33 Posts
Discussion Starter #1
With the high cost of fuel, just how important is it to continue putting the 91 or better grade fuel in the tank?

Also, this has only happened twice (recently) after the car had sat overnight, it was very reluctant to start and it took many cranks to get it going? It had been running & starting great (just did a valve job about 5,000-6,000 miles ago). This morning it started just fine...What should I be looking for???

Thanks!
 

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1991 300 SE
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18,534 Posts
This is just me but I continue to use Shell V power to keep the engine clean, both my gassers run well with it.

If it was cold when it didn’t start right away and warmer when it started right up it could be the cold start injector.
 

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1990 300SE
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1,466 Posts
Turns out that using lower octane fuel is going to retard your timing a bit. Worse efficiency that way. You'll end up paying more for cheap fuel then you would for the good stuff. That is assuming you don't damage the engine from excessive predetonation, as that would be very expensive. I only use Shell V-Power or ARCO. Some techron fuel system cleaner every once in a while.
 

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1990 560 SEL & 1995 E300D
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459 Posts
I couldn't agree more with your statement, danwatt. That also holds true for buying "cut-rate" premium as well......you know which stations in any locale I am refering to. The 10% additional you pay for a good brand of gas over the cut-rate places will result in all of 20% better fuel economy. Trust me, I have documented this for months since owning my W126.

Gary
 

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1,285 Posts
Sure, you can put in the cheap 87 octane stuff. Also, you can urinate into the tank daily to get that little extra out of it.

If you do this in a public place, you may gain new friends.
 

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90 420SEL
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44 Posts
As far as I know,changing to a lower octane fuel won't retard your timing, unless your engine is equipped with a knock sensor and u begin to experience some pinging(predetonation) because of it. I don't believe the older models (W126's) have knock sensors and am going to try using regular fuel in mine soon.I used to run 11:1 pistons on the street before and regular worked fine, although the fuel may have been higher octane all around in them days. Just be careful and listen for any pinging at first.Try it out under full throttle, if it's good, no problem. If it does, retard your timing slightly,until it stops.
I will try it and let u know. I don't think the fuel mileage will suffer much if at all.Also a mix of each is also an option.
 

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1987 420 SEL
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2,095 Posts
You're only going to save a few cents using the cheaper gas anyway! Is that worth messing up your engine?
 

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1987 420 SEL
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2,095 Posts
Deathrattle. Ha! Ha! I gotcha ya! I work in Clinical Trials monitoring new drugs coming on the market.

I just realize that trying to save some pennies in buying lower octane gas is just not the way to go. Why get a MB luxury coupe or sedan that has been recognized around the world and proven for it's high speed and safety performance for many years and then can't pay for the gas. I feel some people should just get an economy car (Geo, Honda, Skooter, etc.)that would give them more mileage per gallon then try and skimp on using quality fuel that the MB's require. Before I purchased my 420 SEL a year ago, I took all that into consideration. Maybe, some others should have also.
 

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1,285 Posts
AMEN!
 

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1987 420 SEL
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2,095 Posts
Hey Deathrattle. Which one is you in your Benzworld picture? And, which pharmaceutical drugs have you or are you taking? He He [:D]
 

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1987 420 SEL
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2,095 Posts
Hey Deathrattle. I know why you were in the trunk. You were back there sniffing some high price petrol weren't you? Ha! Ha! [:D]
 
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