Flubadub hit the nail on the head. As I stated before, car manufacturers don't make a dime by you using premium. They are telling you what the engine needs based on compression and tuning. You more than likely aren't saving anything by using lower octane since your mpg and performance will suffer. There is also the posibility of engine damage if the knock sensors can't compensate enough. Detonation will damage an engine.

As I understand, premium fuel may have 2 advantages.

The first is more performance. In the Netherlands and Germany, premium fuel have additives to keep the motor more clean, and do not increase the RON of the petrol. An investigation of ADAC shows that the effect is negligible: https://www.adac.de/infotestrat/tank...cePageId=49341 (in German)

The second is to keep your motor clean. A Dutch consumer program did some investigation, and motor revision experts say the can't detect any difference of any significance with the cars that they maintain: (in Dutch)

In the second episode, a petrol station employee says that the basic component of the premium fuel is exactly the same petrol, and after delivering an additive substance (1 liter on 10.000 liter) is added. That's about 20-25cl on an average tank of 50 to 65 liter (it can be very concentrated of course). https://www.youtube.com/watch?v=fgC8...=536.863439778

All 'n' all it looks more like a marketing gimmick to sell the same product for more money, and in controlled laboratory conditions measurable effects might be seen. A nice observation in the above documentary is that the premium fuel is said to deliver more performance as well as cleaner engines, but THE way to pollute your engine more is to push more power out of it. If you want to keep your engine clean, your driving habits are more important.

If premium means a higher octane level (e.g. from 95 to 98), the performance increase can be measured, just like 95 to 91 gives less performance.

The are countries where very low quality fuel is being sold, and in such a case it is important to buy "premium" fuel (i.e. at respected companies with a trustable source of petrol).

You were right! I finally had to stop for gas this morning and I checked... it's 91 octane. Thanks for keeping me sane. I hate dispersing wrong information.

I haven't watched that video, as I gather that it's in Dutch, but what you say mostly contradicts what I found when I researched the issue. If you use lower octane fuel than recommended, then you would get worse performance and economy, as the vehicle knock-detection systems would retard the timing to prevent detonation. But everything I read suggested that there were no performance, economy or engine cleanliness benefits to using higher than recommended octane. If someone has hard evidence (not just a a talking head) that there are, I'd be keen to read it. I do agree that the claim that using higher octane fuel than recommended appears to be just marketing.

True, it depends on the motor, not sure if the M274 would benefit from it. E.g. octane 100 seems to exist, but most motors cannot take the benefit out of it.

I found another (Dutch) movie, where it is obvious that the big petrol companies (Shell, BP, Total) get their fuel from exactly the same point, i.e. the basic petrol is not different:

The journalists were fined by the police because they were filming the topic.

It's really interesting to see how the definition of "premium" varies across the globe.

In the US, the difference between regular, mid and premium is only in the octane level. Mercedes specifies 91 octane in the US, and in the US that's premium. If you run lower octane, you will likely give up a little performance and you MAY have problems with knock if the engine management system can't adjust for it. Knock can cause long-term damage.

In the US, EPA requires that all gasoline must contain a specified minimum level of additives (mostly detergents). In the US, there is no difference in the required additives between regular and premium. This minimum level isn't enough to keep most engines gunk-free. The major auto manufacturers (including Mercedes) established a higher standard, called "Top Tier" gasoline, to help protect the performance and emissions of their engines. Look for the "Top Tier" label on pumps to see if you are getting the additional detergent additives. Check the list of licensed retailers at www.toptiergas.com/licensedbrands

This is true in the US and Canada too. All the refineries make each grade of gasoline to meet a specific standard. It all gets fed to common pipelines and pumped into common tanks at distribution centers across the country. Fuel delivery trucks from all the retailers fill up from the same tanks. What's different is the content and concentration of the additive package that gets fed into the trucks as they load. Each of the major retailers has a different additive treatment.

I only put PREMIUM "Top Tier" certified gasoline in our 2023 GLE350 and 2024 GLC300. In the Chicago area, only MOBIL and SHELL are "Top Tier". The Top Tier label is affixed to the pump.

Evidently, Top Tier fuel isn’t good enough anymore.
Along come the new kid on the block, Top Tier+ fuel.
Emphasis on the plus!

What are the differences?

Thanks. I didn't know about this. After researching a bit, it looks like all/most brands nor offering Top Tier will/have moved to the Plus formulations.
Found a link - https://www.toptiergas.com/gasoline-brands/

I recall the "Super Shell with Platformate" TV commercials that aired in the '60's. Shell gasoline was promoted as containing this miracle mileage enhancing fuel additive, and the commercial showed two vehicles -- one with Shell with Platformate and the other without Platformate -- driving across a desert, where the without Platformate vehicle coasts to a stop and the with Platformate vehicle drives on for several more miles. Shell had to pull the ads when it was revealed Platformate was nothing more than its proprietary name for tetra-ethyl lead, which was in every gasoline brand. Oil companies have always been scoundrels.

Actually, Platformate was different from tetra-ethyl lead, and actually enhanced fuel economy. It was an additional ingredient that was created over a Platinum catalyst.
Most manufacturers have a proprietary additive that they advertise.
Today, Shell is advertising "V-Power NiTRO+." Nothing wrong with that, in my mind.

The reason Shell removed those ads was that the cars that ran out of fuel were black and the ones that kept running were white. Dick Gregory, a Black comedian, made a big stink about the "racist" implications of the ads.

Every Brand has some sort of specialty that they advertise, even if may not be exclusive to them.
Esso had a Tiger in the Tank with a proprietary ingredient, but PETA didn't weigh in. They also let Kellogg's Tony the Tiger off the hook.

BTW my cars seem to run the best on Shell. It could be my imagination, it could be that I'm susceptible to advertising, or that the two MPG improvement that I actually see might be true.

Turbocharged and supercharged engines need the proper octane rating more than normally aspirated.
In the case of expense analysis, the money saved on using a lower octane rating in the charged engines, is less than the repair or replacement cost of the engine, and likely shorter than projected engine endurance.

Lower octane in engines from the last 30 years or so will retard the timing. Newer ones will adjust the entire engine mapping to protect themselves.
In either case, your mileage and performance suffers.

You'll get the highest grade detergent packages with the highest grade available, and the "Top Tier Plus" mentioned above is aimed directly at gasoline direct injection (GDI) engines. Which is what we have.

Finding it must be as difficult as finding King Crab Leg buffets these days. I'll perform a few searches to learn why TopTier+ is better, and where to find it. Thankyou for the updated info! 👍
-Allen

Update 10/2/2025 - Here we are: TOP TIER PLUS.
What it is

• Goes beyond EPA standards:
  While EPA standards set a minimum level of detergent additives, the Top Tier™ program and its Plus version set stricter requirements developed by automakers.

• Focus on GDI engines:
  GDI engines operate differently than older engine designs, requiring higher levels of detergency to prevent carbon buildup.

• An advanced fuel standard:
  Top Tier Plus was developed to meet the increased performance and cleaning needs of modern gasoline direct injection (GDI) engines.

SOURCE: https://www.toptiergas.com/performance-standards/

I wasn't aware of the Dick Gregory element of the story. I suspect casting black and white vehicles in the commercial had more basis in the majority of televisions in that era being monochrome, rather than in the advertiser's attempt at subliminal racist propaganda.

Thanks for the WEALTH of useful information! I seem to get the most miles pumped into the thank at Shell stations in St. Louis and further south. The 2022 GLE350 gets at least 530 miles on a full tank with southern Shells. Here in the Chicago area, or Wisconsin, or Michigan, I'm lucky to get get 470 miles on a fill-up. Very strange!