Fuel types

Hi guys,
I was wondering if I could use regular fuel in my Mercedes CLA250?
The Manual says;
“!Only refuel using unleaded premium
grade gasoline with at least 91 AKI/
95 RON.
! Only use the fuel recommended. Operating
the vehicle with other fuels can lead to
engine failure.”
Ive read couple of articles that say its all right to use regular fuel, and it wont damage the engine because of the retard ignition timing.

Would appreciate any advice.
Thanks !

It will probably in all likelihood not cause major engine damage. But I have no idea why you would not use the high octane fuel that your car requires. You have nothing to gain, and lots to lose if in fact it does affect engine operation.

Why would you trust guys on the internet (including us) more than the guys who designed and built the car?

The engine retards the timing when the knock sensor, a piezoelectric accelerometer that sends a pulse at a predetermined frequency tuned to the shock wave when the cylinder preignites, sends the engine control computer a pulse.

Let me simplify it; the engine adjusts the timing when the knock sensor detects a condition that you do not want… a condition that could harm your engine. And in so doing it trades performance for protection. It doesn’t allow the engine to perform the way it was designed to in order to protect it.

So, if you do decide to use regular, know that you’re trading performance and risking your engine just to save a few bucks at the pump. It’s your choice. You’re informed now.

Wow. You had a question, you consulted your car’s “bible,” got told the answer…and now you ask us?

You wrote the answer to your question before you even asked it. Why on earth would anyone buy a luxury car and then fret about the extra $0.30/gallon it takes to properly feed it…ESPECIALLY in light of plummeting fuel prices? That’s like ordering USDA prime steak in Morton’s and asking for some “2 Buck Chuck” to wash it down!

“Why would you trust guys on the internet (including us) more than the guys who designed and built the car?”

Why would anonymous strangers–with both unknown agendas and unverifiable credentials–be more authoritative than the people who designed and built the car?

“Why on earth would anyone buy a luxury car and then fret about the extra $0.30/gallon it takes to properly feed it?”


The difference in cost between regular and premium Is about $0.60/gal around here, and that is $240 extra for each 10,000 miles driven if the car gets 25 mpg. Still, that is no a lot of money for someone that can afford an expensive luxury car. That’s less than $1 a day extra for the right gasoline. I would buy premium if my car required it. Anyone that wants to get 10 or more years of good service from a car should maintain it by the book.

next he will want 22" rims and a killer sound system. what do they call that? murdered out? whew. i must live in kansas. we dont got no cars like that here

As the @the same mountainbike so aptly described, the car will retard the timing to protect the engine with regular gas. As @jtsanders aptly describes, the cost to run premium is pretty small overall. To combine the two thoughts, retarding the timing to protect your engine will reduce your mpg’s likely stealing away any savings you THOUGHT you might have running regular.

Your owners manual has the last word, put premium in your Benz.

What they said. I would use premium in any of the high-output turbo motors that are common now, even those that say ‘recommended’ in their owner’s manual.

Yours says “”!Only refuel using unleaded premium". HOW MUCH CLEARER CAN IT BE???

Using the cheapo stuff and allowing the continuous knock compensation…over and over and over again is purely …and knowingly…asking for trouble.

I blew a hole clean through the top of one piston doing that.


Your owner’s manual uses a legally binding word. “ONLY”! If regular grade fuel was acceptable they would have used a word such as “RECOMENDED”. If your warranty is still in effect use of regular fuel followed by engine damage will surely void it. Using jtsanders calculation which I agree with will save $1,200 in 50,000 miles. $1,200 might pay to have your starter motor replaced but replacing your engine will be 5 times that or more!!!

You bought a MB, NOW you want to cheap out??? The rest of my comments about this are unprintable in a public forum…

You can use regular fuel. It will last until the engine is destroyed. That this will likely happen much sooner than if you used the fuel the manufacturer told you to use should be a factor in your decision. :wink:

On some engines the manufacturer will say “premium recommended”. That means the engineers have designed enough retard into the timing that even if you use regular, the computer can retard the timing enough to prevent pinging. But if the manufacturer says the engine requires premium, that means there isn’t enough retard designed in to guarantee no pinging will occur. And continued pinging will quickly damage an engine.

My advice is to use the gasoline the owner’s manual says to use.

Reminds of the Girl who bought the Supercharged Nissan 4x4 pickup,then sneeringly said She ran regular in it(which probaly put the performance back to NA levels-WTF? Spend a few thousand extra for a premium engine and not use the performance?sometimes I dont get it-Kevin

I can see someone deciding they don’t care about the performance and wanting to save a buck. Maybe they lost their job say and in a financial pinch. But it would be counterproductive if the engine simply isn’t designed for regular. In my area there are three grades, 87, 89, 91.

87 : $2.25/gallon
89: $2.35/gallon
91: $2.45/gallon

So there’s not much price difference, certainly not enough to risk damaging the engine.

87 : $2.25/gallon 89: $2.35/gallon 91: $2.45/gallon

So there’s not much price difference, certainly not enough to risk damaging the engine.

Where you live.

Cheapest gas near me.

87 - $1.93
89 - $2.20
91 - $2.40

But I agree - if the manual says you must use premium…then use premium.

Here’s what I don’t get?

People go out and buy a 50K, 60K 70K…etc vehicle, and then when they find out they MUSTuse a higher octane gas, or a 100% synthetic oil they baulk?

I wish I had those kinds of problems.


I’m usually the odd man out and don’t necessarily agree that the use of less than 91 means instant death all the time. Per the usual, it depends.

On a normally aspirated engine a lower octane can be safely run in many cases with no issues.
This model Benz is turbocharged I assume so in a forced induction engine you should stick with 91 or higher.

Call the Benz dealer and price a new long block. That would probably lead to hugging and kissing that Premium pump… :smile:

Manufacturers tune up procedures on old cars would tell you to advance the timing until you could hear detonation under load. Doesn’t apply to today’s engines.