Mercedes S-Class at the gas station

Mercedes S-Class: Regular or Premium Gas? (2024 Guidelines)

If you’re a Mercedes S-Class owner, you might have wondered which gas you should use.

And in that case, this article is for you!

Mercedes-Benz recommends premium gas with a minimum octane rating of 91 for the S-Class. This is to ensure optimal engine performance and longevity. However, if premium gas is unavailable, the S-Class can safely take regular gas (87 octane) or mid-grade gas (89 octane) temporarily.

By the end of this article, you’ll clearly understand why these recommendations exist.

So, let’s start!

At a Glance: What gas type does your Mercedes S-Class need?

Before diving into the details of octane levels, let’s get straight to the answer many of you might be looking for.

After all, sometimes, all we want is a straightforward response, right?

  • For a regular Mercedes S-Class: A regular S-Class like the S400 or S450 needs premium gas (91 octane), according to the owner’s manual. However, regular gas (87 octane) can also be used temporarily.
  • For AMG or high-performance models: Mercedes-AMG or high-performance models like the S600, S63, or S65 require premium gas of at least 91 octane. However, Mercedes-Benz recommends 93 octane gas for optimal performance.
  • Tuned Mercedes S-Class: If you’ve given your Mercedes S-Class an ECU tune (for example, using a RaceChip), fill it up using premium gas (at least 91 octane).

Quick note: Occasionally filling up with regular (87 octane) or mid-grade gas (89 octane) won’t necessarily damage your car. But if you want the best for your vehicle long-term, sticking to the recommendations is the way to go.

If you prefer a table overview, here is what you should know:

CategoryTypeIs It OK?Notes
GasRegular (87 octane)!Safe to use temporarily, although prolonged use might impair engine longevity and performance.
GasMid-grade (89 octane)!
GasPremium (91 octane)Recommended octane rating by Mercedes-Benz, which can prevent knocking sounds and prolong the engine life.
GasPremium (93 octane)
GasEthanol-based (E10)Same as the typical gas at most pumps.
GasEthanol-based (E15)!Not optimal for the car, but it won’t be a danger in the short term. It can only be used on S-Class models from 2005 or newer.
GasEthanol-based (E85)!Mostly not OK. It can only be used if your Mercedes S-Class has a flex-fuel system.
GasReformulated Gasoline (RFG)A type of gas that burns more cleanly, about 30% of the gas sold in the US is RFG. (Source)
AdditivesFuel injector cleaner!Be careful; it can potentially damage the engine when overused.
AdditivesOctane booster!Be careful; it can damage the engine when misused.
AdditivesFuel stabilizer!Be careful; it can damage the engine when misused.

Stick around if you’d like a deeper dive into why these recommendations exist. Otherwise, happy driving, and treat that Mercedes-Benz well!

Reader’s tip: 6 Best-Looking Wheels For Your Mercedes (OEM & Aftermarket)

Does the Mercedes S-Class require regular or premium gas?

Time to dive a little deeper!

According to the Mercedes S-Class owner’s manual, premium gas (91 octane) must be used for maximum engine output and longevity. However, if premium gas is not available, regular gas (87 octane) can be used temporarily:

Mercedes S-Class owner's manual - recommended gas type

That means you risk prematurely damaging the fuel system or engine by continuously using regular gas (87 octane).

Similarly, the engine of the Mercedes S-Class is designed to reach its rated performance and fuel consumption values with premium gas (91 octane).

Tip: The correct gas type for your Mercedes S-Class will always be written on the inside of the fuel filler flap.

Mercedes S-Class fuel filler flap gas type indication

If you own an AMG model of the Mercedes S-Class, like the S63 or S65 AMG, premium gas (91 octane or higher) is a must.

While one tank of regular (87 octane) or mid-grade gas (89 octane) isn’t the end of the world, consistently using this gas type can lead to issues like engine knocking, reduced power, and even potential long-term engine damage.

Mercedes S-Class S550 filling up with gas at Marathon station

And what about a tuned Mercedes S-Class?

Modifications like RaceChip can significantly increase the power of your Mercedes S-Class. But when you upgrade the engine’s performance, its gas needs an upgrade too.

Just as an athlete on a rigorous training regime needs specialized nutrition, a tuned Mercedes S-Class requires premium gas (91 octane or higher).

Difference between regular, mid-grade, and premium gas

Fueling up might be a mundane task, but there’s a science to it.

Behind each pump, there’s a lot of chemistry going on to make our vehicles run smoothly.

So, if you’ve been wondering, “What do these octane numbers mean?” let’s take a look!

The octane rating of a gasoline type indicates its resistance to premature detonation or knocking.

In car terms, knocking is a rattling or pinging sound you’d hear when the air-fuel mixture in the cylinders detonates earlier than it should. It’s not good for your engine!

The higher the octane rating, the more compression the gas can withstand before it ignites, which reduces the likelihood of knocking and leads to smoother engine performance.

When you’re filling up, you will typically see the following gas types:

  • Regular gas (87 octane): Regular gas is the most common and least expensive type of gasoline available at most stations. It’s best for everyday vehicles that don’t demand high performance.
  • Mid-grade gas (around 89 octane): As the name suggests, mid-grade gas sits between regular and premium gasoline in terms of performance and price. Perfect for those who want higher-quality fuel without paying too much.
  • Premium gas (91 octane and above): Designed for high-performance engines, this gas resists knocking and ensures smoother combustion. It’s best for high-performance vehicles, luxury cars, and those with turbocharged engines.

The main difference between regular, mid-grade, and premium gas is that regular gas has an octane rating of 87, mid-grade gas has an octane rating of 89, while premium gas has an octane rating of 91 or higher.

Regular (87 octane), mid-grade (89 octane), and premium (93 octane) gas at a pump

High-end cars (like Mercedes-Benz models) often have advanced engines that run on relatively high compression ratios. These engines thrive on the richness of premium gas, offering better acceleration, fuel economy, and longevity.

Real-world experiences with Mercedes S-Class gas choices

Not convinced by the benefits of premium gas? Let’s check out some real-world experiences from Mercedes S-Class owners!

1. Knocking due to regular gas

Here’s a story from a Mercedes S-Class owner who experienced engine knocking due to using regular gas:

I accidentally filled up with regular the S550 started to knock. I was down to a quarter of the tank and as soon as I was able I added more Premium. Now that the tank has been refilled with premium it does not knock


2. Making a mistake when filling up

Here’s an S-Class owner who found out their dad filled up the car with regular gas instead of premium:

Ok so I let my father borrow my 2003 19,000 mile S55 today and in re-payment he did me the favor of filling up my car……

I was on my way home and decided to do a routine tunnel run, my first pass to 100mph went flawlessly, slowed down to around 50mph and decided to run again…. car downshifted with zero power, it was like driving my girlfriends c230, embarrassed to the nsx beside me, i pulled off the freeway and decided to open my data logger, and dl the last run made.

HUGE amounts of timing retard, I called up my father and asked him what gas he used, “REGULAR son, you know I don’t believe in all that octane mumbo jumbo” he replied.

Previous to this I never realized what a drastic difference it would make in such an application. However after an ecu reset and fuel dump and refill I am now a believer that the difference is huge.


3. The difference isn’t always noticeable

On the contrary, here’s someone who uses regular gas in their S-Class and has had no issues so far:

I’ve been using “regular” gas easily for the last 100,000 miles, if not more, with no issues.


Can you use ethanol-based fuels for the Mercedes S-Class?

Ethanol-based fuels are fuels that contain ethanol, which is a renewable fuel made from biomass. Biomass consists of a variety of plant materials.

It looks something like this:

Corn put into the gas tank filler cap of a car

That’s a joke, of course!

In reality, over 98% of gasoline in the US contains ethanol. The most common ethanol-based fuel is E10, which consists of 10% ethanol and 90% gasoline.

Ethanol-based fuels reduce air pollution, but at the same time, using gas that contains a high concentration of ethanol can damage your vehicle.

E10 is a standard that’s commonly accepted to be safe for most cars on the road today, including the Mercedes S-Class.

However, you may occasionally find E15 gas containing 15% ethanol and 85% gasoline. In the US, E15 can be found in 30 states at over 2,400 pumps (source).

E15 is not optimal for the Mercedes S-Class, but it won’t be a danger in the short term. However, it can only be used for Mercedes S-Class models from 2005 or newer.

Mercedes S-Class filling up with gas, front view

Once you increase the ethanol percentage further, it really won’t be too good for your car.

For instance, E85 gas is also available in some places, but it can only be used for your Mercedes S-Class if you have a flex-fuel kit.

FAQs about gas for the Mercedes S-Class

If you have any more questions about which gas type to use for your Mercedes S-Class, take a look at these FAQs:

What happens if I accidentally use regular gas in my Mercedes S-Class?

Filling your Mercedes S-Class with regular gas once won’t cause immediate harm. However, you might notice reduced performance and engine knocking. To prevent potential issues, it’s a good idea to top off with premium gas on your next fill-ups. Consistently using regular gas isn’t advised, as it can lead to premature engine wear.

Can I use fuel additives for the Mercedes S-Class?

You can use fuel additives or cleaners for the Mercedes S-Class. However, it is important to carefully read the manual beforehand and avoid using additives more than twice a year, as this can damage the engine or fuel system.

Can the Mercedes S-Class take 93 octane gas?

Filling up a Mercedes S-Class with 93 octane gas will allow it to extract its maximum performance and engine longevity. However, 91 octane is just as good unless you have a Mercedes-AMG or a high-performance model.

Final verdict

To summarize: You can temporarily use regular gas in the Mercedes S-Class, but it’s highly recommended to use premium gas for the long term.

Mercedes-Benz recommends premium gas to preserve the engine and ensure your S-Class continues driving as it should for years to come.

Sure, in the short run, you might save a bit by using regular gas. But think about the long game: lower fuel efficiency and potential repair bills.

Suddenly, those upfront ‘savings’ might not feel so significant.

If you have any more questions, let us know in the comments!

Gas requirements for other Mercedes models

Are you interested in the required gas type of other Mercedes-Benz models?

If so, you can find everything you need to know in the following articles:

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