Do any of you guys use mid grade gas? (89 octane)

[Lend27]

I'm going to use Premium during the break in period, but did any of you try to use an 89 octane mid grade after break in? Len in NC

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[NYCGLK]

no, only BP ultimate for mine. What's the point of having engine engineered for premium and using regular gas?

[wired]

how would you know it won't hurt using mid-grade.. besides.. mb says it's engineered for premium.. does anyone really know it's true unless we're driving f1 race cars.. just a thought..

thanks

[guyfromtor]

Here are my 2 cents:

1) If MB says you need premium, they know best.

2) If it was safe to use lower octane, would it not be best for them to say so, would it not be a selling point?

If you consider the price difference between mid grade and high grade per tank, we are not talking huge amounts. Unless you do very high mileage per month.

I waiting for my GLK to arrive, I am goign to be filling it with premium. To each his own

[F18BEN]

Now here is my 2 cents----- If you own the car use premium. If you lease it use regular. I lease my E350 with the same engine and it has never seen high test only regular. I have 20K and no problems. The engine runs as good as my GLK...

[MKenM]

I OWN my GLK and use mid grade 70 to 80% of the time. I will tell you that from a performance standpoint premium is much better but I get 20 to 22 MPG on mid grade with no problems.

[wired]

based on performance.. does that mean you get lower fuel consumption on using premium compared to mid-grade..

thanks..

[NYCGLK]

maybe the case is computer detunes engine to adjust for lower octane so you have slugish engine which in turn makes your driving more fuel efficient.

[paul65k]

Originally Posted by NYCGLK

maybe the case is computer detunes engine to adjust for lower octane so you have sluggish engine which in turn makes your driving more fuel efficient.

This is exactly what happens with modern engine/fuel injection technology. Premium fuel is a necessity if you are trying to make 75% or better horsepower from your engine, for normal driving where you typically make 30 - 50% power regular is fine, 50 - 75% mid grade and if you have a heavy foot then it's premium only for you!!!

If you were Mercedes you would be crazy not to recommend the highest grade fuel possible for ALL driving as this is much too complicated and in reality how many of you would really hold back if you wanted to pass and get everything you could from your car at that moment??

Most of us would never know the difference using lower grade fuel, and the likelihood or damage is minimal at best, but in the end who wants to take that chance so...................for me it's premium only unless it's not available for whatever reason and then I drive accordingly as outlined above!

[mac911]

They often put more cleaners in the Premium too. Since you need the high octane anyway, think of the extra cleaners as an extra benefit.

Truly, how much would mid grade save you in a year? With the price of gas, it's about 3 percent.

If you spent $2,000 on gas, you might save $50 or something?

$50 to help ensure the cleanliness and performance of the engine annually? Seems like a no brainer.

[RedRover]

Run top tier gas and the cleaners are the same in reg-mid-premium.
www.toptiergas.com
This is the gas recommended by BMW and Audi.

Don't know what happened to MB.

[cyberglk350]

I was going to ask the same question. I live in Denver at 5280 feet. I think the altitude changes Octane requirement.

85 = 87
87 = 89
89 = 91

Is this correct? Do any other GLK owners live in Denver and use 89 instead of 91?

[slk55er]

Originally Posted by cyberglk350

I was going to ask the same question. I live in Denver at 5280 feet. I think the altitude changes Octane requirement.

85 = 87
87 = 89
89 = 91

Is this correct? Do any other GLK owners live in Denver and use 89 instead of 91?

I lived in the Denver area for 29 years and rarely found 91 octane. 89 is just fine at the higher altitude.

[SunMoonRain]

I recently bought a 2007 ML350 and its my first MB, so I am still not familiar with all the features. I filled 89 gas by mistake and now dont know what to do. Will it harm the engine, should I have it drained out? I plan to keep the car for sometime and dont want to damage my engine. I have been reading all the replies on this thread but still not sure what to do.

[GLKKa2H]

Originally Posted by SunMoonRain

I recently bought a 2007 ML350 and its my first MB, so I am still not familiar with all the features. I filled 89 gas by mistake and now dont know what to do. Will it harm the engine, should I have it drained out? I plan to keep the car for sometime and dont want to damage my engine. I have been reading all the replies on this thread but still not sure what to do.

Firstly I think you should try posting your concern i the ML-forum:
http://www.mbworld.org/forums/m-class-w164-72/

On a general basis I would say you can get away with it (don't sue me) without "draining it". The fuel requirement stated in the 2007 ML Operator's Manual: http://www.mbusa.com/mercedes/data/p...g_ml320cdi.pdf,
is minimum octane 91.

However, given you drive your ML carefully, especially not pressing the gas pedal fast and hard, and no extreme speeds, you should prevent engine knocking, which is most likely what can happen at the octane you have filled. Drive in this manner until you are halfway - or 2/3's down in the tank, and proceed with filling gas in accordance with MB recommendation/specification.

[lkchris]

Originally Posted by paul65k

This is exactly what happens with modern engine/fuel injection technology. Premium fuel is a necessity if you are trying to make 75% or better horsepower from your engine, for normal driving where you typically make 30 - 50% power regular is fine, 50 - 75% mid grade and if you have a heavy foot then it's premium only for you!!!

This is exactly the "mythology" believed by many.

There is no adjustment on a Mercedes for use of low-octane fuel.

Read, for example, what your owners manual says:

If premium unleaded gasoline is not available and low octane fuel is used, follow these precautions:

• Have the fuel tank only partially filled with unleaded regular gasoline and fill up with premium unleaded gasoline as soon as possible.
• Avoid full throttle driving and abrupt acceleration.
• Do not exceed an engine speed of 3000 rpm if the vehicle is loaded with a light load such as two persons and no luggage.
• Do not exceed 2/3 of maximum accelerator pedal position if the vehicle is fully loaded or operating in mountainous terrain.

Does this really sound to you like the car "adjusts" and it's ok?

[glkbeige]

I vary the octane ratings and see no difference. I won't be keeping this model more than 3 years because a Hybrid will be out soon. I agree with the lease versus own statement. Check out the below link to a new 3.5L V6 with 24% jump in fuel economy.

http://www.insideline.com/mercedes-b...8-engines.html

[3Stars]

quote: Apparently, under certain circumstances when gasoline with lower than the required 91 octane is used a "mega knock event" can be induced, leading to a complete grenading of the engine LINK

[MBRedux]

You don't need to take my 35 year racing history word, but anyone who uses a mid-grade fuel to putt around town is one thing, but if you plan to drive at interstate speeds or expect to get the maximum in your engine's life and performance, stick with the recommended octane grade designed by the engineers who made your engine.... If you buy a Benz and wish to fuel it like it was a Prius, then you're an idiot plain and simple.

[cyberjak]

I personally never understood people who bought luxury cars then cry about the price of premium gas or having to use premium gas. The difference between 87 and 91 at most gas stations is no more than $0.20 cents a gallon and in some station as little as $0.10 cents a gallon.

If your car tank is 15 gallons were are talking about less than $3 per fill up even if you use 1 tank of gas per week we are talking about $150 difference a year. If you can not afford a $150 a year why the hell are you buying a luxury car any ways over a economy car. Those are the same people who cry about how expensive services are on luxury cars, if you can not afford the service then why are you buying a luxury car in the first place.

I am not putting anyone down just pointing out the obvious. Yes I know plenty of people ni real life who suffer form the above syndrome.

[lkchris]

It's a "culture" thing and lots of 'merikuns just can't adjust.

'merikun culture is a large displacement, low power output (for size) engine

Euro culture is influenced by taxation based on engine displacement and therefore engine sizes are kept small and to get any power the engine must be highly tuned--which means high compression.

A general example is that a 3-liter (183 cubic inches) European engine will basically normally create the same power as a USA 350 cu in engine (5.7 liters), but it will do it with high compression and premium fuel.

High compression engines are more efficient than low compression engines. (See also diesel) Smaller engines burn less fuel than larger engines.

You can't make a sow's ear out of a silk purse.

[QSHIP]

Premium may cost a little more but I noticed you get a better gas mileages in it.

[webada]

Its not just the Octane rating, premium gas (93+) usually contain cleaners which will provide some minor cleaning action to the valves.

We had a case in NY where some gas station was spoofing 93 with 89 or 85 gasoline... several regulars there had to replace their entire fuel system due to long term damage. This came to light because several less than year old cars was sent back to dealerships. This made the local news.

[mac911]

Originally Posted by QSHIP

Premium may cost a little more but I noticed you get a better gas mileages in it.

This is true.

Premium allows the engine to make the power and fuel efficiency it was designed to make.

Interestingly, they actually recommend an even higher octane in Europe.

Go with the 91, if I could get 93, I'd even use that.

[GLKKa2H]

Originally Posted by mac911

Interestingly, they actually recommend an even higher octane in Europe.

It's the number written on the pumps in Europe which is higher, as the octane rating is given in Research Octane Number (RON). Another rating is the Anti-Knock Index (AKI), which may be seen written on pumps as R+M/2 Metod, used in countries like US and Canada.

The difference between the octane rating for RON and AKI will be shown 4 to 5 points lower for the latter - for the same fuel. For instance corresponds the European 95 RON (Regular unleaded), minimum octane rating recommended for the GLK, to AKI 90 - 91.

The European Premium unleaded has an octane rating of 98 (RON).

A third type of octane rating is called Motor Octane Number (MON), which as well has an "offset" with regard to the number for the same fuel, and is another 4 to 5 points lower than the AKI.

And, as the effect of increasing altitude decreases the air density, it consequently lowers the octane rating requirement. Meaning, filling fuel with lowered octane rating at high altitudes could (theortically) cause engine knocking going down to sea level, given the engine management system do not manage it.