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W124 E300 12v 1992 and a 2009 Crown Victoria
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Discussion Starter #1
Hello every one,

We have two types of gas here in Saudi Arabia; 91 and 95. Dunno whither they are ron, mon or pon or even John, so I want to know.

My car is Euro import and the resistor is on "S" position which is, according to the EZL Trim Function Guide, for premium gas. I don't even know what grade (type of octane number) they are referring to with "premium".

I used both grades and had no noticeable difference (or rather I couldn't notice a thing) in performance but I felt like the 95 grade burned faster.

Yesterday I changed the spark plugs and their wires and today I'll fill it up with 95 grade again for may be they were the reason behind the increased consumption over 91 (does this make since).

No pinging, detonation or any other abnormality showed up using both of them.

Having this said, can we conclude at least whither our 91 is premium or normal?
 

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W124 E300 12v 1992 and a 2009 Crown Victoria
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1,044 Posts
Discussion Starter #4 (Edited)
Yup, the 95 one is certainly premium, but I wonder if the 91 one is. In the States there are more than one grade of premium, aren't there?

Gas is indeed cheap here. SR 0.45 = $0.12 US for the 91 and SR 0.60 = $0.16 US for the 95. Prices change depending on the distance from the distribution point(s).

But nah, it only compensates for other expenses. The internet for example; 4mb ADSL costs $66 US here.
 

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1993 300E, 2003 996 Turbo X50
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624 Posts
I IMed my friend and he said he was definitely measured using RON. 91 RON would be regular 87 octane gas then.

Where I am we have 87, 89, 91 or 93. I use 93 since thats what's at Shell. Some sunoco stations have 91 and 94 octane, but usually only one grade of premium.
 

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W124 E300 12v 1992 and a 2009 Crown Victoria
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Discussion Starter #6
Hmmm, thanks for the confirmation.

In the Euro W124's manual (link here, page 128) it says that the minimum is 95RON/85MON. I believe this means the left side equals the right side. I would like to know what kind of xON is for the 87 you mentioned to correspond to 91RON, just to enrich my background.

On a side note, I heard that the xON in the states is measured by the average of RON+MON (RON+MON/2) and it is called Pump Octane Number.
 

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1993 300E, 2003 996 Turbo X50
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624 Posts
Yep or its more commonly called AKI (anti-knock index). The 87 octane I got from the 95 RON is the AKI number. You can basically figure that AKI is RON minus 4 (roughly). Mercedes recommends 91 AKI or 95 RON as you stated.
 

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W124 E300 12v 1992 and a 2009 Crown Victoria
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Discussion Starter #8
Cool.

I have one last question and I'll stop bothering you again. I promise :)

From time to time I use 95RON (one or two fills maximum) and then back again to 91RON. Sometimes I don't find the latter. Is this bad for the engine? Should I change permanently to one if them, specially that using 91 (87AKI) proved to not cause knocking?

Ooops, those are more than 1 question :)

Thanks again for your co-operation.
 

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1993 300E, 2003 996 Turbo X50
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624 Posts
My car runs far better on the higher octane, so thats what I use. That said it will run on 87 fine with just a slight loss in power and fuel economy (my observations).
 

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W124 E300 12v 1992 and a 2009 Crown Victoria
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Discussion Starter #11 (Edited)
Thanks for the link man. But unless I missed something after reading it thoroughly, I couldn't find an answer to my question that I change fuel grades from time to time. Does it hurt or does the engine only run the way it does with each grade?

And BTW, I dunno if my Euro W124 comes with a knock sensor. However, I'm sure that it has an EZL CAT dial set to S (750 Ohm), even-though it refused to budge when I tried to change it.

One more FYI, here we have MBs imported from all over the world; US, JPN and Euro, plus our own local dealer's. Each have their fuel grade tuning and reports on how they behave towards different grades of gas (we call it Benzene here) were very inconsistent from different users.

Starting this point, I guess the topic is getting out of hand. I would understand if no further replies are done.

Thank you all for spending your precious time here :)

My car runs far better on the higher octane, so thats what I use. That said it will run on 87 fine with just a slight loss in power and fuel economy (my observations).
Sorry, I clicked on reply before yours was registered.

Mine had do difference except that the higher grade consumption rate was either same or higher. Does not make sense I know.

Things really are getting out of hand.
 

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89 300E; 00 E320
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2,515 Posts
Thanks for the link man. But unless I missed something after reading it thoroughly, I couldn't find an answer to my question that I change fuel grades from time to time. Does it hurt or does the engine only run the way it does with each grade?
Quote from Jonathan "You can run 89 in an M103 on stock ignition timing w/o issue."

w/o issue means it wont hurt.
 
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