Recommended Fuel Octane
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Junior Member
Joined: May 2010
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From: Phoenix, AZ
2008 ML350 4Matic
Recommended Fuel Octane
Ok, here's a good one. Now I'm certain that everyone has been educated on this subject, but this guy hasn't so please lend your knowledge to the newbie.
My '08 ML350 owners manual states that I should use nothing but high octane (92) fuel in my car. Ok, I understand it's necessary as the factory documentation states, but is it absolutely required? Will my engine fall out or will it explode if I sneak in 89 octane once in a while? What would happen if I run 89 octane all the time?
My '08 ML350 owners manual states that I should use nothing but high octane (92) fuel in my car. Ok, I understand it's necessary as the factory documentation states, but is it absolutely required? Will my engine fall out or will it explode if I sneak in 89 octane once in a while? What would happen if I run 89 octane all the time?
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Joined: Mar 2008
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ML320CDI 2008 all options inc air suspension
Ok, here's a good one. Now I'm certain that everyone has been educated on this subject, but this guy hasn't so please lend your knowledge to the newbie.
My '08 ML350 owners manual states that I should use nothing but high octane (92) fuel in my car. Ok, I understand it's necessary as the factory documentation states, but is it absolutely required? Will my engine fall out or will it explode if I sneak in 89 octane once in a while? What would happen if I run 89 octane all the time?
My '08 ML350 owners manual states that I should use nothing but high octane (92) fuel in my car. Ok, I understand it's necessary as the factory documentation states, but is it absolutely required? Will my engine fall out or will it explode if I sneak in 89 octane once in a while? What would happen if I run 89 octane all the time?
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From: Albuquerque
'10 CL550, '12 GL550
The words "recommended" and "specified" have two different meanings.
For Mercedes, premium is specified.
https://mbworld.org/forums/attachmen...june06star.pdf
For Mercedes, premium is specified.
https://mbworld.org/forums/attachmen...june06star.pdf
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Joined: Dec 2005
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From: Pennsylvania, USA
2011 GL450, '06 R500 traded, '08 ML350 sold
And they ruin the motor and when they get stuck with a huge repair bill they blame the brand.
Folks! MB does not get a kickback from the oil companies to say Use Premium gas ONLY.
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Joined: May 2010
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From: Phoenix, AZ
2008 ML350 4Matic
Hey, Ninjajim, it's not a matter of saving 3 dollars at the pump since I drive that particular car only about 4 thousand miles per year. It's a matter of me having lent the car to a visiting vice president of my company who drove it around for 2 weeks then revealed to me during our ride to the airport that he only put in mid range gas since he's done the same from day one with both he and his wifes car without any issues. Both of which happen to be, you guessed it, Mercedes. I've been putting in 91 octane since driving it off the lot, but wanted to know if there was any wisdom hidden within his statement. For you to presume another motive was a waste of your time.
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2009 ML350
at the risk of sound uncivil here.. WTF are you talking about??
you ask this:
and this:
first, what other motive could there POSSIBLY be to switch from premium to mid grade, when you clearly know your car is supposed to run premium? gee, how presumptuous of me 
secondly, no there is no wisdom here, your VP is not only a cheap ***, but also an inconsiderate one and you shouldn't let him drive your car anymore.
you ask this:
secondly, no there is no wisdom here, your VP is not only a cheap ***, but also an inconsiderate one and you shouldn't let him drive your car anymore.
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From: Pennsylvania, USA
2011 GL450, '06 R500 traded, '08 ML350 sold
Owners manual states that if for some reason premium fuel is unavailable to use the highest grade possible. A while back I was out of town and was running out of fuel. The service station I found was put of premium so I bought two gallons of regular so I can make it to the next station where I filled up with premium. So, just try not to use low octane unless you have no choice and then try to limit the amount consumed. As a previous poster said there are sensors that adjust themselves for proper burning and the engine is not as efficient. Btw your boss IS cheap!!!
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From: Phoenix, AZ
2008 ML350 4Matic
There is no doubt that the guy's a cheap *******, and yes, I should not have loaned him the car, but what's done is done. I was thinking that by my posting what I did, I would be able to learn something and perhaps even get the facts about a topic that not only I, but perhaps other people were thinking of. To have someone state "I don't understand why people buy these cars but then want to get away with saving 3 dollars at the gas pump" didn't help me get any closer to obtaining the information that I was looking for, nor did it help anyone else.
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Joined: Dec 2005
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From: Pennsylvania, USA
2011 GL450, '06 R500 traded, '08 ML350 sold
Let me put it another way. The car will function but not at its optimum performance. It's like someone smoking a cigarette. One won't do harm but over time...
Thread Starter
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From: Phoenix, AZ
2008 ML350 4Matic
Perfect analogy. I'd like to send my boss this string to show him what he's actually doing, but he's the kind of guy that tends to only listen to himself. That and of course I called him a, well, you get the picture.
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300E a couple 1994 w124wagon E320 Wagon/,1971MGB Track/Rally, MG Midget Autocross ,2000 E320 wagon.
Maybe your
boss is from Denver where 89 is equal to high test.
With your heat and 1000ft altitude 91min will always pay in performance and mpg gained v.s. the savings he tried to achieve with the odds being he is not living above 5000ft.
He will be working for you someday
With your heat and 1000ft altitude 91min will always pay in performance and mpg gained v.s. the savings he tried to achieve with the odds being he is not living above 5000ft.
He will be working for you someday
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2009 ML350
if you can't read between the lines (a valuable life skill), that means put what you're supposed to put in your car. i guess i could have said it's going to retard your timing and pre-detonate under load, but the bottom line is exactly what i said. don't be cheap (the only reason you would do this, outside of exceptional circumstances). if there is some other motive, i'd like to know what it is.
BTW, i think if you framed this question differently we'd have been having a different conversation. obviously as is, there's no way i could've known, but nonetheless i apologize for presuming your boss' cheapness was your own
Last edited by ninjajim4; Oct 6, 2010 at 10:33 PM.
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From: Los Angeles
2005 C55
It should be fine, my dad did that to my car once and when I asked him why he told me thats what they put on all the cars. He works for Mercedes at the shipping facility near long beach. I still always use 91.
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ml 320
I have read in the owners manuel using lower grade fuel doesn't burn up all the fuel. unburned fuel ends up in the caytalic converter which eventually clogs it up resulting in lost power and having to replace it.
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From: Delmarva
2010 C300 Sport 4MATIC 2011 ML350 4MATIC
Here's a little twist to this. We bought my wife a C300 and have been putting in the top stuff ever since bringing it home. I even educated myself on the "Top Tier" designation and only buy the 93 from the listed companies.
This past Monday we picked up a ML350 for me. So in talking to the sales rep... the SALES REP no less. He says something like "Oh that's no big deal. I get a new one every year or so, on lease and never put the good stuff in it. I only put the cheapest stuff in it." So I'm thinking, well you lease it buddy. What do you care? I keep my vehicles for a very long time, and don't want to take a chance at hurting the performance of the engine, sensors, or possible repairs.
To take a little angle on the "save $3.00" comment, I do look at it this way; If the cheap stuff costs $1.75, and the premium 93 top tier costs $1.95 and I get ten gallons, then it really is only $2.00 more to buy the good stuff and keep my beloved Benzes running at their designed peak performance. That's the way I look at it. It's not very scientific, but rather practical to me.
We buy the premium synthetic oil for the engines, so we should buy the premium fuel too the way I look at it.
http://www.toptiergas.com/
This past Monday we picked up a ML350 for me. So in talking to the sales rep... the SALES REP no less. He says something like "Oh that's no big deal. I get a new one every year or so, on lease and never put the good stuff in it. I only put the cheapest stuff in it." So I'm thinking, well you lease it buddy. What do you care? I keep my vehicles for a very long time, and don't want to take a chance at hurting the performance of the engine, sensors, or possible repairs.
To take a little angle on the "save $3.00" comment, I do look at it this way; If the cheap stuff costs $1.75, and the premium 93 top tier costs $1.95 and I get ten gallons, then it really is only $2.00 more to buy the good stuff and keep my beloved Benzes running at their designed peak performance. That's the way I look at it. It's not very scientific, but rather practical to me.
We buy the premium synthetic oil for the engines, so we should buy the premium fuel too the way I look at it.
http://www.toptiergas.com/
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From: Nova Scotia, Canada
2023 GLK250, 1987 560SL
Use the grade of fuel your engine is designed for. It's a no brainer: higher compression engines require more refined fuel.
Fuel should be ron+mon/2 = 91
Some retailers only post ron, others mon; most ron+mon/2.
Higher octanes than what the engine is designed for offer no benefit because there is actually less stored energy.
Fortunately, modern engines are smart enough to detect knock and can adjust accordingly, but you do run the risk of going into limp mode.
Fuel should be ron+mon/2 = 91
Some retailers only post ron, others mon; most ron+mon/2.
Higher octanes than what the engine is designed for offer no benefit because there is actually less stored energy.
Fortunately, modern engines are smart enough to detect knock and can adjust accordingly, but you do run the risk of going into limp mode.
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Mercedes Benz ML350 4MATIC W164
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From: TX
2023 GLE3502W, 2024 GLC3002W, 1967 Pontiac GTO 4 sp (sold...sniff)
The compression ratio in our '14 ML350 is 12:1. The compression ratio in my 1967 Pontiac GTO is 10.75:1. While I have never tried to run gas at less than 93 octane in the Goat, the timing has gone out sometimes and the knocking sounds like someone was dumping ball bearings into the cylinders. As stated above, your engine will adjust to the lower octane. You won't hear the knocking because the knock sensors adjust the timing to prevent it, but you'll lose a certain amount of power, which won't be really noticeable either. Proof of that is you didn't mention feeling it. I have never seen any published about the long term effects of running less that prescribed octane in a newer car. I would like to know who decides whether 91 as recommenced on my gas tank filler cap is available vs 93. In Texas where I buy gas the highest octane is 93. We went to the Winstar Casino in OK last year, and the gas station on premises had 91 as the highest. You would think that might be less expensive than 93, all else being equal. Who decides what's available, 91 or 93? I buy 93 at the local Costco. This past Sat 93 was $2.75. On the way to golf on Monday, a local station had 87 for $2.49 and 93 for $3.39. For those of you who deride someone for looking to save money, we are targets for ripoff artists. 20 gallons would be a $13.00 diff between Costco and the local. I'd cheerfully put 2 gals of regular in my car to avoid getting my pocket picked.
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From: Albuquerque
'10 CL550, '12 GL550
