MB gasoline - regular vs premium

[MaximaGuy]

The MB from my signature calls for premium gas, was wondering why regular won't work.

Other owners chime in - other than premium results is less knock, anything out of the ordinary that regular fuel won't work.

 

[Aichiguy]

Knock can damage an engine. Surely on an 18 there's a knock sensor that causes the computer to retard timing to alleviate this which would result in lower performance.

 

[Nick1994]

12:1 compression ratio, and a price tag that start at like $60k.

 

[bbhero]

Ahh a higher compression motor is very likely the reason for needing the higher octane gas. And if you have money to buy or lease a MB then why worry about an extra 50-60 cents a gallon. A extra $10-13 per fill up from dead empty really going to break the bank for you?? I hope not.

I do not mean to give you a hard time here. Just thinking about it all. Really difficult to understand why when people buy or lease a expensive vehicle they suddenly cringe about having to put "expensive" gas in the expensive vehicle they just bought or leased. And don't expect your tires or other needs for that vehicle won't be expensive as well. Because they very likely will be.

 

[MaximaGuy]

Concur its not breaking my wallet.
BTW knock and retardation is under load or heavy acceleration and regular driving conditions one never knocks under normal loading.
Curious if the vehicle is designed to only take premium, my Lexus takes regular

 

[Wolf359]

Yes, just read the manual. Says minimum octane is 91. Not sure if Texas has 93 or 91. If you had 93, you could make a mix of regular super to get 91. There's usually a section in the manual that says if 91 isn't available, use 87, but not to give it wide open throttle and use a light throttle and fill up as soon as possible with super.

 

[Andrew1972]

Besides the power loss expect a mpg loss of vehicle requires premium.

 

[bbhero]

Still it is a higher compression motor... Being that is what it is.. it could very possibly knock even under "regular" acceleration if running regular gas in a motor with that high a compression. Heck my Nissan Altima 3.5 VQ has a 10.4:1 compression motor and it is set to run the best on 93. Says so in the manual. I'm glad that extra $10-12 ain't hurting you too bad at all. That's a very good thing

 

[slacktide_bitog]

It's DI. Use premium

 

[Trav]

Questions like effects of detonation on direct injectors and combustion chamber deposits due to retarded ignition timing come to mind.

 

[aquariuscsm]

Your engine will ping under heavy acceleration on regular unleaded.

 

[Stevie]

Originally Posted By: MaximaGuy
The MB from my signature calls for premium gas, was wondering why regular won't work.

Other owners chime in - other than premium results is less knock, anything out of the ordinary that regular fuel won't work.


My Last MB SLK Supercharged the owners manual said only use premium or engine damage "WILL" occur.

My 2013 SLK says use premium fuel.

It's a Mercedes! Use premium and enjoy the premium ride.

 

[oldhp]

24.6 gallon fuel tank. Lets say you let it run down to 4.6 gals in the tank. Manual says 91 or higher octane fuel. So if you mix 6 gals 87 octane plus 14 gals 93 fuel you get 91 octane, and you save $3.00 per tank figuring .50 cents a gal savings. At $3.00 per tank per week, 52 weeks a year you would save $156.00 a year. I don't about you, but having to mix fuel to save $156.00 ain't worth it.

 

[Omahaug]

Quote:
BTW knock and retardation is under load or heavy acceleration and regular driving conditions one never knocks under normal loading.

What's "regular driving conditions"? Because you know it's not just the car but also a host of other variables that are different.

Like summer and winter blends and even the temperature of the engine, fuel or air which is seasonal. If they designed it for 91, going to 87 may not be enough to account for other variables.

 

[ruhroh]

Your car will adjust the timing to prevent knock, but the small fuel economy loss might take out the savings from not running plus/premium anyway.

 

[SZR48207]

You wouldn't wear a hemp belt with Italian Wool pants, and you shouldn't use 87 octane in a Mercedes Benz.

You gotta pay to play baby.

 

[Trav]

Originally Posted By: ruhroh
Your car will adjust the timing to prevent knock, but the small fuel economy loss might take out the savings from not running plus/premium anyway.


It will prevent it from happening AGAIN during this drive cycle if its within its parameters, it will not prevent it.

 

[Kestas]

I switched from premium to regular on my Mercedes ever since they started gouging drivers with the price on premium. It used to be 5 or 10% more, now it's 27% more.

 

[djb]

How many drivers use the full power output of the engine? I doubt very many or very often.

And it's not certain that the engine is going to knock on 87 octane, or that there would be a noticeable loss in fuel economy. Since, all else being equal, 87 octane has a higher energy content, the fuel efficiency might actually be better. (In real life this is overwhelmed by the ethanol fraction, which might go either way depending on the blend.)

>> "It will prevent it from happening AGAIN during this drive cycle if its within its parameters, it will not prevent it."

That's not how the ECU works. It detects the onset of knock while it's still below the level of perception and damage. It immediately adjusts the timing and perhaps adjusts the mixture to limit the knock, but it doesn't persistently change the settings.

 

[Ducman]

Originally Posted By: MaximaGuy
Concur its not breaking my wallet.
BTW knock and retardation is under load or heavy acceleration and regular driving conditions one never knocks under normal loading.
Curious if the vehicle is designed to only take premium, my Lexus takes regular



You are rather mistaken.
And both vehicles mentioned are different animals.

Knock can vary in intensity and the ECU will be able to detect it before you ever will.
The ECU will do what is necessary to avoid the condition because it must prioritize efficiency in order to comply with emissions targets and any knock what so ever is absolutely detrimental to that goal.

As an example.
Our family has two hacks that are C180 Kompressor sedans.
The manual states that they are capable of running on 91 Octane(RON).
Whilst it's absolutely true up to a point and for all intents and purposes and it's all good to the uninitiated, the reality is very different.
I had to demonstrate this case to my lovely wife over a period of time as she used to run the 91 octane being the wise and frugal gal she is.
When we first met, her vehicle was for all intents and purposes, mechanically sound in every respect but I couldn't for the life of me work out what was wrong with it's performance as the shift points and nature of the shift was terrible in my experience(NAG 1 transmission).
It was the first MERZ I had ever had anything long term to do with and it constantly left a sour taste in my mouth. I was always pointing out the issues I was having with it to her as we drove anywhere in the vehicle.
Then one day we were out on a long drive and needed to refuel as we were nearly empty.
I said i'm over this may I try a little something.
She agreed and I said i'm going to put some 98 octane in it to see if that makes the car a better drive,
I put a full tank of 98 in it and drove off down the road.
Probably within 2-3 kms I noticed the nature of the shifts of the auto improve almost like flicking a switch. Even my wife could notice the difference sitting in the passenger seat and commented on it.
An added bonus was the average fuel consumption stared to trend down to make quite a respectable difference over the next 60 or so Kms. Whilst not openly cost effective with the 98 we decided to continue with using a premium fuel of no less than 95 octane going forward as it was apparent it was better for the car.

The lesson for you in this example.
Follow the manufacturers recommendation. The Germans aren't stupid even though they may have a fiddle here and there, and now and then.
If they say to use the top fuel in the Owners manual. it's probably for a good reason, like it or not.