I have driven cars that "require" premium gas for over 20 years as all high end performance automobiles do but for the first time ever I actually had a more serious issue so for me these endless posts about it being a scam are over for the V8 S class anyhow. Case settled for me.

I always put in premium in my S Class and have in prior S classes as well but yesterday morning I was on fumes and after dropping my daughter at school I pulled into the closest station who only had at the time regular and mid grade which is 85 and 87 I think in Colorado. I filled about 3/4 of a tank with their 87 which was too much in hindsight and went on my way. Car drove fine but later in the day I noticed some misfiring and then the check engine light came on. It stayed on and the misfiring continued. Very sluggish and delayed response but the car drove better at higher speeds was not as noticeable as at slow speeds and in particular with acceleration from a dead stop being very bumpy. I then went to Costco and filled the remainder with premium in an attempt to thin out the low grade fuel. Eventually the CIL turned off and the car is driving fine again.
So for a S560 if you end up in a similar spot put in just enough gas to get you to a better refueling option and don't do what I did.
FWIW - my Lexus LX570 also says premium but it has never once impacted that car and I have read that numerous times so we always put in regular and it is A-Ok. My Range Rover Supercharged (which is their supercharged V8 and not the smaller supercharged V6) is not as bad as the Mercedes V8 but you can definitely feel it. So for some cars the label does indeed mean something.
I hope this helps and if someone else has a similar issue they can avoid the time and headache of a dealer visit by burning the low grade gas out and adding premium ASAP helps you as well.

 

So, I'm kinda curious. I'm not recommending to use less than premium when it's recommended for the car, but what was the reason the gas station didn't have premium? I'm asking, because gas stations only have two tanks. One for regular and one for premium. Mid-grade is created at the pump by mixing regular and premium. So if they were out of premium then they couldn't have had mid-grade, either, and you ended up filling with 85, which is too low. I believe the minimum is 87 on these engines. Typically regular is 87 and mid-grade is 89, but Colorado is different.

 

Its the turbocharging. Like you found on your Lexus LX, naturally aspirated its really no big deal, I drove Lexuses before also and you could run regular, but I would never put regular in the S560 or anything else with a turbocharger.

 

For the record, I have been using mid-grade gasoline in my S-600 since it was new without a single stumble. And I live at 600 feet above mean high tide.

 

Modern cars have sensitive knock detectors which continuously monitor for pre-ignition and adjust timing to protect the engine.

The risk of using low-octane fuel is not damage to the engine but degraded performance in terms of power, fuel economy, emissions, running smoothness, etc. When a manufacturer says a car 'requires' premium, I think they're saying that's the optimum fuel for the full range of design considerations.

I've experimented with mid-range gas on a few occasions and the car ran just fine, but I mostly use 93 in order to get the full benefit of the Mercedes engineering.

 

Not the case with the S560. That was the reason for my post.
I had a S550 before and like you never had an issue if I ever ended up with a lower tier gas in it which was rare but it did happen. On my 2019 S560 it started with obvious misfiring, the car actually felt bumpy if that makes sense. Very slight bumpy but you could feel it and it was more pronounced for me as the driver than for my girls but they started to feel it too. And the CIL glaring at me on the dash.

I turned off the car and immediately restarted and it was still doing it - no change and no reset of the timing or anything. The car did not adjust with its fancy anti-knock sensors or at least it did not in a way that worked. Later on after the car sat in the garage for maybe 30 minutes I drove to go mix in the premium fuel. The light was still on but it drove ok and later the light went off.

So while potentially anecdotal and not scientific my experience was one I would not want again, but if it happens to you it could be that cheap gasoline.

 

It also could have been bad gas

 

Basically, if you are not pressing on the throttle pedal more than ½ way, a0 the turbos aren't spooled up, and the combustion pressures are not high enough to need above-mid-grade gasoline. If you do press the throttle to the floor, you likely do need high-test gasoline.

 

It’s a $120,000+ Mercedes. Put the right fuel in it lol

 

OP you purchased 3/4 tank of craptastic gas. What you experienced for misfires and the like had little to do with lack of octane. Bet it smelled of old paint thinner to boot. You’re lucky it didn’t spoil fuel injectors.

Here in Phoenix I get to deal with high ambient temps reducing power. Always give her super. Temps get under 80 and missing horses are found.

 

I too came upon a gas station that only sold the 87 octane after they struggled to keep water out of the storage tanks underground for the mid grade and high grade gasoline. Even the buttons on the gas pumps were removed with only a functioning button for regular fuel (87 I think). I've never seen this before so I just drove off and went to another gas station. My previous W222 was a 2017 S63 and it had a moment of misfiring after I filled up somewhere out of town. Misfired twice and bogged down to the point being frightening. Went to the MB service bay and they didn't see anything wrong. May have been bad gas because it never happened again. I think the other posters are correct in that the cars with turbos DO NOT like anything less than premium high grade. OTOH, my 2019 S560 (no longer own it) never had an issue at all since it was only given 93 octane.

 

Same here, I was using regular fuel in my Mercedes-Benz and a couple of times the car stumbled and had weird problems .It turned out to be a turbo pressure valve failure or something like that .Having switch back to premium fuel I had no more weird issues

 

The turbos have alot to do with it, but it was most likely bad fuel. I would run some Chevron fuel addative and full tank of top tier premium and you will be good to go. Costco works well. Big turnover in fuel, and properly maintained. My old 2008 S550 could use 87 in a pinch, but not the w222.

 

I have a 2013 M3. Anytime I put gas in less than premium I get a CEL and Increased Emission message. I don’t notice any decreased performance. I used to gas up at Kroger but put in “premium” a couple of times and got the CEL/Increased Emission message. This told me I was paying for premium gas but not getting premium gas. Since then I have stopped using Kroger gas and have had no more CEL issues. I bought my 2015 S600 in May and only use Shell or Cosco premium with no issues. I haven’t even tried less than premium in the S600.

 

Hint: Buy gasoline from places that are affiliated with gasoline manufactures:: like {Shell, Conoco, Texaco, Chevron, Phillips,...} in a pinch buy from stations no more than one step away from a gasoline manufacture, but never stoop to unbranded gasoline {Walmart, Costco, 7-11,...} and when you do have to in a pinch, put in the best grade you find on the pump.

 

What do you know about Top Tier gas? I have heard positive things about Top Tier gas and use Costco gas because it is a Top Tier gas.

 

I would use Top Tier gas for sure

 

Top Tier is recommended by pretty much all premium brands and I wouldn't fill anything else. It basically has additional detergents that particularly help keep the fuel injectors from clogging. Unfortunately with the dawn of direct injection engines the cleaning agents have lost some of their values as the fuels no longer wash the back of the valves, but a clogged or leaking fuel injector is a potential expensive repair.

https://www.toptiergas.com/licensed-brands/

 

I used to work in fuel logistics, 15+ years ago (in the UK), and wanted to share my experience.

It's typical that a refinery/terminal is owned by one company, let's say Shell, but you will see Chevron, Esso, Shell and other trucks pulling fuel out of that location, it was what we used to call back hauling, and it was a part of an exchange agreement. In exchange for allowing other companies to load fuel in our terminals, we were able to load fuel in their terminals, in areas where we have gas stations, but no storage.

The base fuel that was loaded into the trucks was all the same, there wasn't separate storage for each company, it all came from the same single source, the only difference was the additives that were added to the fuel at the time of loading. It's these additives that are a companies differentiating/sales/marketing factor.

Then we move onto to super markets/grocery stores, these guys don't have their own fuel terminals, they are in the business of selling groceries, fuel is just an added draw to get customers through the door. So how do they get their fuel? They go to the same terminals as everyone else, and they buy the same base fuel, and possibly even some additives (maybe their own, maybe something from the company who they bought the fuel from), these guys only used to sign 3 month deals, and were always shopping for the next low rate.

I'm no longer in the fuel business, and things may have changed, but I doubt it, as the number of refineries and storage locations (particularly in the US) is decreasing, these companies are not building net new terminals.

Personally, I have been buying Kroger gas for years, and I have never had any issues related to it in any of my cars (Mercedes, BMW, Porsche, Jeep, Inifiniti, Nissan). The one time that I have had a bad fuel related issue, was when buying regular unleaded from a lonesome Shell station on a road trip (and Shell are on the Top Tier list posted above), but I suspect it was related to the crap in the tank at the gas station, rather than the gas itself.

 

Yes, it's obviously in the additives. Not sure that's much of a revelation. Crude oil is crude oil and we are all burning the same resulting hydrocarbons. It's the additives such as ethanol to boost octane and detergents to keep the engine clean. How much of all that stuff and what specific stuff is in there ultimately differentiates the fuel. State regulations such as here in California also result in different blends. Emphasis on blends. All fuels pumped at gas stations are ultimately blends of raw fuel and additives.