Improviz

I would ask the moderators for a bit of latitude here. For one, I have been accused of lying, and for two, this is an issue which I feel should be cleared up; if someone were to follow the poor advice being given, they could be the proud owner of a damaged, unwarranted vehicle--not good. I will not engage in any name-calling, even if provoked.

So, let's look at what Mercedes has to say on the subject. The following are direct quotes from my 2001 CLK55 Owners Manual, Warranty Booklet, and Service Booklet.

Beginning with the Owners' Manual: first, on page 11, there is a subsection entitled "Operating your vehicle outside US or Canada":

Clearly, they regard fuel with a low octane rating as improper for the vehicle.

In case that leaves any doubt, there is the portion quoted previously:

05C55 claimed that that his owners' manual does not state "Caution!" in this section, and impled I'm lying. His may not, but mine does; see attached image.

Thirdly, there is the part I introduced thusly:

O5C55 claims that this is under the "gasoline additives" section and is only applicable to additives. However, this is not true: the statement is clear: Damage or malfunctions resulting from poor fuel quality OR from blending specific fuel additives are not covered by the Mercedes-Benz Limited Warranty.

OR means "either". If either condition is met, the warranty is voided. And clearly, when the manufacturer states that:

1) Premium unleaded fuel MUST be used;

2) fuel with a lower octane rating is "improper fuel";

3) damage caused by poor fuel quality voids the warranty;

Then their meaning is abundantly clear.

But wait, there's more:

They also mention fuel quality in the warranty booklet.

That's right: on page 14 of the warranty booklet, in the section entitled "Items Which Are Not Covered", it is explicitly stated:

They also mention it again, under the emissions warranty (page 23):
And as if that wasn't enough, it is also mentioned in the service booklet (pages 8-9):

The boldface in the following quote is as it appears in the service booklet (page 9); red portion is colored by me for emphasis:
The "special precautions" are the quote provided initially by me, re-quoted near the beginning of this article, and appearing below (along with the "Caution!" portion that 05C55 accused me of making up) in the scanned page from my owners' manual.

Bottom line is this: Mercedes is quite clear that 1) using regular unleaded fuel can damage the engine; 2) if it is used, and the engine is damaged, they will not pay for it.

Use at your own risk.

AaronC

Yeah, on any high performance FI engine you have to run Premium. MB should not be responsible for ring, piston, or valve damage because of detonation. It is not their fault that an engine is toast becasue somone put the wrong octane in.

AaronC

BTW, I just read the other thread, and I totally disagree with you 05C55.

Since you dont believe that your motor is adversly effected by low octane gas, do this for me.

1. Make sure you have 1/8th tank of high octane gas in your C55(the previous fillup needs to be 93 as well) and do 3 runs on a dyno at a reputable shop. Then have them do a compression and leak down test. This is your baseline.

2. Fill your tank up with 87 octane gas and do 3 runs on a dyno at the same shop. Then do a compression and leak down test. Then post your results. If you dont lose 30ft/lbs torque between the runs, and lose compression I will give you a call personally and tell you that you are "The Man" AND pay for your runs on the dyno.

Simple as that.

noka

It would be clear to anyone who can read and comprehend English what the fuel requirements are according to Mercedes. Anyone who wants to do otherwise does so at their own risk. There certainly is enough information in this and other threads, not to mention the manuals, that Improviz quoted from, for people to make their own educated decisions. One things is clear. I would not buy a used car from anyone who did not follow the manufacturers recommendations, assuming I would be able to determine that. However, I know at least one person I would not buy from.


Rgds,
Norm

05C55

You were not even reading a current manual and you misread it. You misrepresented it here on the forum, and you are quoting from a 4 year old manual from a CLK in the C forum. 4 years is a long time in the automotive world, things change. In addition to the fact that you are inciting me you are giving the members of this forum the impression that the use of gasolines less than 91 octane will without question damage the motor and I feel this is not only not accurate but a bit of fear mongering. The 2005 c-class manual does not use the word caution, it is not even in bold print. It does not say that use of lower octane fuels will damage the motor nor does it imply that their use would void the warranty. The section that you are referring to relates to the use of additives and specifically the prolonged use of poor quality fuel which do not contain additives and can lead to carbon deposits. I would recommend that the members read the manual for themselves and make their own determination.

Improviz

I quoted what it says, in plain English. I would argue that you're deliberately misinterpreting it.

Yes, they do: since that time, the compression ratio of the motor has been raised, from 10.5:1 to 11:1. Meaning that the engine still requires premium unleaded fuel, even more in light of its higher compression ratio, per the data provided before from the gasoline faq and other sources.

No, I am attempting to correct the deliberate spreading of disinformation in which you are engaging. To wit:

Absolutely false. I have cited material which says it *can* damage the motor, including direct quotes from Mercedes' manuals, and that it will result in lowered performance and fuel economy. In other words, no good will come of using it, and potential harm can come of it.

You, on the other hand, have claimed that 87 octane fuel can be used without harm to the motor. This claim is directly contradicted by Mercedes' Owner's Manual, Service Manual, and Warranty Booklet, along with other sources, which I provided to you here and here. Sources you have provided to support *your* claim: Zero. None. Nada. Zip.

So who is giving the false impression here? Answer: you.

Your mischaracterizing both what I've said and what the Mercedes manuals state, repeatedly, is what's inaccurate. As to "fear mongering", this is patently ridiculous: I am reporting what the manual and other reputable sources say. You are engaging in cheap debate tactics: shooting the messenger, spinning what the manual says, misinterpreting it, and in a particularly sad example, deliberately trying to deceive your fellow forum members by selectively quoting the gasoline faq rather than ceding a lost point. Which, as anyone can see, is because the facts are not on your side, and so you relentlessly try to massage them or deflect attention from them.

But facts are stubborn things.

Mine does state that the use of lower octane fuel can damage the engine, in the service booklet, as quoted in my first post and again in this one. Further, the warranty manual specifically states that the warranty can be voided for failure to follow the procedures in the service manual, which include the directive to use 91 octane fuel. Your warranty and service booklets do not mention this? I doubt it.

Could someone else please have a look at their warranty and service booklets, specifically the sections I mentioned before, and comment to this? For obvious reasons, I don't really trust 05C55's judgement and veracity here.

Absolutely false. I quoted from the owners' manual, the warranty booklet, and the service booklet, and all are quite clear. Who is "mischaracterizing"? You are. The portions I cited from these booklets are not solely related to this in any way, shape, or form, as can be seen by examining the page I scanned above for starters, along with the warranty booklet and service booklet, which explicitly states (for the second time) that:

Note that it explicitly states that damage to the engine could occur if premium unleaded fuel is not used. How can it be put any more plainly than this??

It is also becoming quite clear that the only interest you have here is not admitting you were wrong, no matter what evidence is provided. I honestly believe that I could provide you with a signed, notarized letter from the CEO of Daimler/Chrysler and the person at AMG who built your engine, and you would still try to argue the point, because it is simply not in your character to admit that your claims were wrong, evidence be damned. And so your disinformation continues...

So would I.

CynCarvin32

I want to know what has changed in the last 4 years to make the internal combustion engine function without the proper grade fuel. This must be the same school of thought that said you no longer need to break a motor in, that you don’t need to change the oil every 3-5k miles, and that the transmission fluid is good for the life of the car.

Things have not changed. The companies that make the cars are trying to lower ownership costs with extended service intervals and you want to cheapen it even more by using crappy gas. Do as you wish but let the next owner know you screwed the car up.

PS. talked to a friend at MB who was been with the firm for 35 years and was schooled in Germany. He said to watch out because the procedure to see why a motor failed or why a serious issue occured includes a fuel test, a test to see how old the motor oil was at the time of the failure and a reading of the ECU. So if your motor fails and you don’t have 91 or greater oct fuel in your car, watch out for the bill be forwarded your way. Enjoy

SaabTuner

This is relatively simple: Drive below manufacturer's stated octane at your own risk.

The octane specifications are simple as well:

93 octane- Represents the octane where, even in the worst reasonable conditions, full ignition advance is achieved.

90 octane- Represents the point where, in severely bad contions, the engine would begin to detonate despite ignition retard.

You just have to decide how extreme the conditions will need to be in order to elicit a detonation reaction. If you guess wrong, you get these:



Adrian~