looney100

Arrie, you are right. George is wrong.

In most newer vehicles, knock sensors will inform the ecu when knocking is occurring, which will cause the engine to retard timing, and take other steps to reduce cylinder temps and eliminate the knocking. It's these interventions that rob one of power if they are using gasoline with too low an octane rating.

looney100

Why change which gasoline you're putting in the truck? If it runs optimally well in 87, why wage the money in 89. If it doesn't run well in 87, why ever put it in?

Abrown3mtg

I go to the same gas station every time. 93 is about the same price as 91 at every other station in the area. Tonight I lucked out and it dipped.... filled at 2.69/gallon

aaacsdai

Arrie's correct, a common example of premature ignition is when the vehicle is turned off and it keeps running-short duration-because the cylinder is still hot, limited fuel is available, with insufficient spark. This is a common occurrence with poorly tuned Air-Cooled engines, Porsche-VW.

looney100

A phenomena known as "dieseling" because it's essentially how Diesel engines work.

aaacsdai

Looney100, exactly.

markgm

I haven't been able to notice any difference in the timing, but I don't have it hooked up to scientific equipment, so take that for what it's worth. I get gas pretty much everywhere (Costco, Sunoco, Shell, Valero), so I'd be surprised if it's not what it's labeled.

rediesel

In my truck I use a higher grade every once in awhile for the better detergents and additives. I only use 91 or 93 in my Benz.

Abrown3mtg

I forgot to add that I feel like the car has a bit more power with the higher grade and have noticed a more efficient burn (could be impacted by environmental influences) while on an all highway cross country trip with lower octane fuel. As is such I've made it a habit to fill with the 93 by my house

Arrie

The problem with engine not stopping was an issue during the old days when cars did not have fuel injection. Carbon build-up in the engine cylinders could be glowing and act as the spark plug and keep the engine going with low octane fuel even when it was turned off at the key. To stop the engine you had to put it on gear and let the clutch up quickly. This would not work with an automatic though...


The cleanup procedure for the engine was simple, run the engine hot and then, with the air filter removed from the top of the engine, spray water in the intake. Did not have catalytic converters so no problems with the "stuff" coming loose from the cylinders.

looney100

Check if your usual filling spot has Top Tier gasoline. If so, the higher octane fuel is unlikely to have a higher detergent content. Top Tier fuel standards stipulate higher detergent concentrations in all grades than most were putting into premium beforehand.

JohnAJohnson

How good is your hearing Jeff? After a long Air Force career mine is terrible. My Corvette requires premium but from time to time I'll put in a tank of regular. Everything is fine unless I load the engine (climb a steep hill in a high gear, etc.), and then my wife will tell me the engine "is pinging". Pinging is bad and enough of it will damage your engine (destroy piston crowns, valve and head issues, etc.). Each engine is unique and will tolerate octane levels differently. Try some regular and keep a close ear out. At the first signs of pinging, go to the mid grade, and continue to move up to the octane necessary to eliminate the pinging.

And feel free to ignore the "if you can afford a Mercedes" crowd. It gives the writer a warm fuzzy without adding anything at all to the conversation.

Firenza

I only put 98 for my E350. And I also tried 95+ but couldn't feel any difference....!!

El Cid

If DAG had not designed the engine to operate on 91+ octane, they would not REQUIRE it. Simple as that.
It is harmful to engine and decreases fuel efficiency to use less than 91 octane.
Also, it would be a tremendous advertising boost for MB to say its vehicles can run on regular or mid-grade gasoline. But they don't, because the cars can't without probability of damage and lower fuel efficiency.

CarolinaBluetec

I only use 93 octane in my E350 and SLK320. Just filled up for $2.39/gallon. South Carolina may have crappy roads, but at least they don't have crappy roads and high taxes.

JohnAJohnson

Things aren't always as simple as they seem. While I agree with your logic, isn't it possible that some MB cars will run just fine on a lower octane fuel, and that MB is practicing CYA?

Have we become so risk averse that questioning the defacto is grounds for ostracization?

beejAMG

^ I agree with El Cid on his logic. John, you can try to use below 91 by all means but at your own risk. if nothing breaks after a few years, good on you. for me, a few dollars everytime i fill up is less worries down the road. besides, its a fact that the higher the octane, the better it burns and more efficient the cars gets. so why should i take the risk of filling below 91 and save a few dollars when it burns faster and run the "risk of ruining" my engine? nothing but 98 for all my cars btw.

cetialpha5

In the manual it does say that in emergencies if there isn't any premium available, you can put in regular. It just tells you not to accelerate hard and not to drive at the maximum speed and not to use more than 2/3 throttle if fully loaded. If you have 93, you can mix 1/3 regular 87 with 2/3 super to make a 91 octane mix.

Octane is the ability to resist pre-detonation. I believe MB has knock sensors that would retard the timing if it senses knocking which is pre-detionation. Retarded timing will decrease power, however the BTU content of super and regular are about the same. So higher octane doesn't really burn better, it's more the opposite, it resists detonation until the spark sets it off. In terms of efficiency, you're already at peak efficiency unless timing is retarded. You should just read the wiki on octane rating.

I think in other forums there are people who mention that they just use regular all the time instead of super. It's probably fine as long as you don't go full throttle and drive gently.

Jeff RoTull

Why I'm bothering to contribute to a six year old thread, I don't know, but why do people assume that everyone who owns a car bought it new or can afford it new? I took possession of my mother's 2009 E350 20 months ago. It's just hitting 30k now and anyone with about 10 grand can own it according to book value. I couldn't buy a car for half what she paid for this initially (just for the purpose of going to the store and doctors' appts)

By the way, as I write this I'm at the shop where they're finishing up my 30k.. This is third mechanic that's told me the car's in great shape. It's never been filled with anything but regular for the life of the car. Performance aside, I think this stuff about regular gas ruining the car is just motorhead masturbation.

El Cid

If you cannot afford the proper fuel, perhaps you should trade it in on something that does run on regular.
M-B would not manufacture a car that could run on regular, but then say it required premium. Neither would the other companies that manufacture engines requiring premium fuel.
If you use regular, you lose power because the engine computer recalibrates to run on low grade fuel. You also lose fuel economy for the same reason. The engine uses more gas to do less.
I live in South Carolina and we have 87, 89 and 93 octane gas. I generally run 93 octane, but will occasionally add 89 which sort of averages out to 91, but not precisely. Always fill up at 1/2 tank mark.
Incidentally, if it is a 2009, you might want to pursue this discussion in the W211 thread. The W212 E350 was introduced as a 2010 model, although you could purchase one in late 2009.

KEY08

Well, I learned from this necro thread that premium was $4.50/gal in 2013. 8 years later, not so bad.

rapidoxidation

Higher compression cars require fuel that is less prone to detonate (premium) or the computer will do as was said above and compensate for it by retarding the timing.
As far as being able to afford a 60K car, the price of admission is just that: What it takes to get into the car. Keeping it running (properly) and maintained is where one begins to understand the cost of maintenance on a Benz is not equal to the cost of maintenance on a Honda. Because it isn't a Honda. I could've bought a new Subaru for what I paid for an 8 year old Benz with 50K on it. The benz is superior in every way except ground clearance.

BTW, ethanol free 91 octane for the Benz and ALL the small engines around the house (motorcycle, chainsaws, generator, weedeater, blower, etc.).

Edited to add some more: I wouldn't be able to afford to own my 2 benz's if I didn't know or be willing to learn how to work on them. I'll be changing all the front end ball joints on the '05 tomorrow. Did the rear springs a few weeks ago.

nc211

I think the debate gets a little more color when considering the introduction of the direct injection instead of port injection. I use only premium, and I buy a fuel treatment off Amazon by the case load and use that too in an effort to reduce the ethanol influence. All I known is my cars run like a champ, and my w212, for as heavy at it is, get better gas mileage with this 3.5 liter V6 than my 2015 VW GTI with its 2.0t 4 banger. Not much better, but equal to better. I think that’s pretty amazing and shows how little amount of fuel is needed per firing sequence of the cylinder..

MBNUT1

Yes

BenzV12

I did when I used to own a W212 .I had to do it because I had a Carlsson Kit in my car and low gas could cause some turbo pressure problems