What kind of gas!
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From: Albuquerque
'10 CL550, '12 GL550
All gasoline-powered Mercedes since 1985 require premium gasoline.
Just as it states in your owners manual.
This is not a conspiracy, it's a design requirement.
https://www.mbwholesaleparts.com/Sta...June06Star.pdf
Just as it states in your owners manual.
This is not a conspiracy, it's a design requirement.
https://www.mbwholesaleparts.com/Sta...June06Star.pdf
MBWorld Fanatic!
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From: Philadelphia area
2010 ML550, 2010 E350 4M, 1966 Corvette Convt C2
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From: Kelowna, BC
'09 ML550
The only way to find out for sure is to try it.
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MBWorld Fanatic!
Joined: Nov 2001
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From: Philadelphia area
2010 ML550, 2010 E350 4M, 1966 Corvette Convt C2
Actually, that is debatable. Most modern high-compression engines like those made by Mercedes push the envelope so far that they operate right on the point of preignition, relying on knock sensors and computer controls to adjust mixture and timing on the fly, thus protecting the engine. Sometimes using a higher octane will, in fact, give better performance, particularly under high-load conditions. But going more than one or two points higher would certainly be a waste.
The only way to find out for sure is to try it.
The only way to find out for sure is to try it.
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Senior Member
Joined: Oct 2008
Posts: 359
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From: Kelowna, BC
'09 ML550
Actually the engine was designed to give maximum rated power on 91 octane. If in fact there is a difference using a higher rated octane which I have been told is not so by engineers it will be so insignificant that its not measurable nor can it be felt by a driver. The only varible in this equasion is the tolerance used by the fuel mfgerer in refining and I do not know what that is but I have been told again that it is insignificant as far as performance of the engine.
The octane rating on US gas pumps is an average between two different ways of measuring it. The only guarantee is that the fuel will be a minimum of the stated rating; it is not unusual for refiners to mix in higher octane fuels depending on what is coming out of the distillation process. That in turn depends on the nature of the raw product going in -- it varies hugely.
Like I said: the only way to find out for sure is to try it. Even if a higher octane makes no difference to your vehicle's performance, it won't do any damage while you are trying it out.
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From: Philadelphia area
2010 ML550, 2010 E350 4M, 1966 Corvette Convt C2
Once again, that is debatable! Mercedes engines are not, in fact, designed for 91 octane, they are designed for 93 octane (Euro spec) and then detuned slightly for US conditions and fuel. "Detuning" may consist of little more than minor tweaks to the ECU mapping. "Car" magazine in the UK tested a number of modern vehicles with higher-octane-than-required fuel and found that some showed no noticeable difference in performance while others shaved up to half a second off the zero-to-60 time. If half a second doesn't sound like much, it means the faster car gets there 40 feet ahead of the slower one.
The octane rating on US gas pumps is an average between two different ways of measuring it. The only guarantee is that the fuel will be a minimum of the stated rating; it is not unusual for refiners to mix in higher octane fuels depending on what is coming out of the distillation process. That in turn depends on the nature of the raw product going in -- it varies hugely.
Like I said: the only way to find out for sure is to try it. Even if a higher octane makes no difference to your vehicle's performance, it won't do any damage while you are trying it out.
The octane rating on US gas pumps is an average between two different ways of measuring it. The only guarantee is that the fuel will be a minimum of the stated rating; it is not unusual for refiners to mix in higher octane fuels depending on what is coming out of the distillation process. That in turn depends on the nature of the raw product going in -- it varies hugely.
Like I said: the only way to find out for sure is to try it. Even if a higher octane makes no difference to your vehicle's performance, it won't do any damage while you are trying it out.
As for the US vs Euro MB's there may or may not be a difference and if there is it is most likely in the chip as opposed to mechanically in the engine. For all that I know euro 93 may be equal to US 91. I just do not know.But performance of the 2 MB's is equal if not exactly the same.
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From: idaho
gl 450
I had my ML 550 into the dealer this week to do the campaign on rubber plugs on the heads that leak oil and have to be replaced. While talking to them they brought up to me that above 5000 feet MB engineers had told them to run only 85 octane. It seems that many of the vehicles here operate above 6000 feet and will not start when it is below 0 in the winter with high octane gas. THey start much easier with 85 octane.
MBWorld Fanatic!
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From: Philadelphia area
2010 ML550, 2010 E350 4M, 1966 Corvette Convt C2
I had my ML 550 into the dealer this week to do the campaign on rubber plugs on the heads that leak oil and have to be replaced. While talking to them they brought up to me that above 5000 feet MB engineers had told them to run only 85 octane. It seems that many of the vehicles here operate above 6000 feet and will not start when it is below 0 in the winter with high octane gas. THey start much easier with 85 octane.
Junior Member
Joined: Sep 2007
Posts: 61
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From: idaho
gl 450
The guy who told me about the gas has been selling MB for over 40 years and is very knowledgable. I too wondered about it but will have to give it a shot next winter. I myself never had a problem getting it started in the cold.
Senior Member
Joined: Oct 2008
Posts: 359
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From: Kelowna, BC
'09 ML550
Octane rating has nothing to do with power. It is a measure of a fuel's resistance to burning. Higher octane fuels can be compressed more than lower octanes and will resist spontaneously igniting ("pre-ignition", "knocking") for longer. It is the higher compression that extracts more energy from the fuel, not the octane rating. Newer technologies such as piezo direct injection allow better control over the flame spread and so can capture even more energy from the same amount of fuel.
I can see no reason why the octane rating of a fuel should have any effect on the engine's ability to start, regardless of the air density. (Higher elevations have lower air density.) During cold starts, the engine computer richens the mixture slightly and automatically compensates for variations in air mass. It is only during normal operation that air mass has any effect on performance -- less air means, in effect, you are running a smaller engine. That is why turbocharged engines are affected much less by elevation: the turbo just keeps pumping until the air mass dictates that the wastegate should be opened.
If the manufacturer says to use 91 octane fuel, you should use 91 octane! Lower octanes will probably not do any damage because modern engines have such sophisticated knock senors, oxygen sensors, and computer control, but you will definitely lose power. Going to a lower octane at higher elevations means you will lose even more power. I live at 4,500 feet, so I live with this every day.
I can see no reason why the octane rating of a fuel should have any effect on the engine's ability to start, regardless of the air density. (Higher elevations have lower air density.) During cold starts, the engine computer richens the mixture slightly and automatically compensates for variations in air mass. It is only during normal operation that air mass has any effect on performance -- less air means, in effect, you are running a smaller engine. That is why turbocharged engines are affected much less by elevation: the turbo just keeps pumping until the air mass dictates that the wastegate should be opened.
If the manufacturer says to use 91 octane fuel, you should use 91 octane! Lower octanes will probably not do any damage because modern engines have such sophisticated knock senors, oxygen sensors, and computer control, but you will definitely lose power. Going to a lower octane at higher elevations means you will lose even more power. I live at 4,500 feet, so I live with this every day.
MBWorld Fanatic!
Joined: Nov 2001
Posts: 4,260
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From: Philadelphia area
2010 ML550, 2010 E350 4M, 1966 Corvette Convt C2
Octane rating has nothing to do with power. It is a measure of a fuel's resistance to burning. Higher octane fuels can be compressed more than lower octanes and will resist spontaneously igniting ("pre-ignition", "knocking") for longer. It is the higher compression that extracts more energy from the fuel, not the octane rating. Newer technologies such as piezo direct injection allow better control over the flame spread and so can capture even more energy from the same amount of fuel.
I can see no reason why the octane rating of a fuel should have any effect on the engine's ability to start, regardless of the air density. (Higher elevations have lower air density.) During cold starts, the engine computer richens the mixture slightly and automatically compensates for variations in air mass. It is only during normal operation that air mass has any effect on performance -- less air means, in effect, you are running a smaller engine. That is why turbocharged engines are affected much less by elevation: the turbo just keeps pumping until the air mass dictates that the wastegate should be opened.
If the manufacturer says to use 91 octane fuel, you should use 91 octane! Lower octanes will probably not do any damage because modern engines have such sophisticated knock senors, oxygen sensors, and computer control, but you will definitely lose power. Going to a lower octane at higher elevations means you will lose even more power. I live at 4,500 feet, so I live with this every day.
I can see no reason why the octane rating of a fuel should have any effect on the engine's ability to start, regardless of the air density. (Higher elevations have lower air density.) During cold starts, the engine computer richens the mixture slightly and automatically compensates for variations in air mass. It is only during normal operation that air mass has any effect on performance -- less air means, in effect, you are running a smaller engine. That is why turbocharged engines are affected much less by elevation: the turbo just keeps pumping until the air mass dictates that the wastegate should be opened.
If the manufacturer says to use 91 octane fuel, you should use 91 octane! Lower octanes will probably not do any damage because modern engines have such sophisticated knock senors, oxygen sensors, and computer control, but you will definitely lose power. Going to a lower octane at higher elevations means you will lose even more power. I live at 4,500 feet, so I live with this every day.
MBWorld Fanatic!
Joined: Nov 2001
Posts: 4,260
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From: Philadelphia area
2010 ML550, 2010 E350 4M, 1966 Corvette Convt C2
Selling MB cars for 40 years speaks highly for the individual as a sales person but has nothing to do with a technical point such as octane to use. MB who has been making these cars and engines for perhaps twice the length of time or more than the guy you spoke to selling the cars says 91 octane fuel is suggested and their statement is backed by years of engineering data and design data says the opposite. Who would you believe?? Perhaps next time you can ask the guy who has swept the shop for 40 years or the cashier who has taken your money for 40 years!
Junior Member
Joined: Sep 2007
Posts: 61
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From: idaho
gl 450
It was MB engineers who sent out the broadcast to this dealership to do this. Not the salesman recommendation. I always have run 91 plus octane and still will since I have not had any problems with starting. I live at 5500 feet.
MBWorld Fanatic!
Joined: Nov 2001
Posts: 4,260
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From: Philadelphia area
2010 ML550, 2010 E350 4M, 1966 Corvette Convt C2
I sincerely doubt that the suggestion came from MB engineering. If so there would be an official TSB and there is none that I can see that address this issue.If you have this or can get it please post it for others to see. What I believe is that your contact was feeding you lots of BS. You, on the other hand are doing the correct thing by using 91 octane.
