I use 91 from cheveron,thinking move down to 89?any advise?thanks in advance

 

91 or higher. Nothing less. It's what the dealer recommends and I'd stick with it seeing as it's a premium car after all. I think this was discussed already, in a rather....fiery debate elsewhere. Might wanna search for it. I'm sure others have good reasons too. Ie. Better fuel economy and engine maintenance.


Edit: See what I mean by fiery? :O

 

Not this one again...

You save no money because lower octane will give you worse fuel economy and lower performance and can damage your engine.

If one can't or doesn't want to spend merely $3-4 extra per fillup, I would suggest not buying a Mercedes.

 

I give you a clue.

What do you think we think of you for asking a question that already has been posted on MBWorld numerous times without searching for an answer first?

You are #1. Thats what we think of you.

 

its only few cents difference per gallon, go all out, you drive a Mercedes, lower grades of gas can cause issues (i think permanent), it will give you less miles per gallon

 

Sell the C300 and buy a Prius.

 

hehe, lets not throw stones, he is rather new to the forum.

I have always used 91 octane Chevron in all my cars, including the non premium cars. Many people will argue that there isnt much difference, but there must be a reason why its more expensive. The higher octane will give you more horsepower and better fuel economy (though both are probably too marginal to calculate). If you arent that pressed for cash, I wouldnt bother switching.

 

thanks a lot bro,much appreciated everyone,let's finish this topic

 

Not so quick...it is more expensive because of the amount of additives used to raise the octane level. Higher octane gas is actually harder to make burn. If your car is not designed with a high compression ratio and doesn't need higher octane fuel, you WILL NOT get more power or fuel economy from using "premium" fuel. You will also not have a cleaner engine as the amount of detergent added to the fuel doesn't change with the octane level.
Driven lightly to moderately, you shouldn't notice a difference in power or fuel consumption between the fuels. Driven harder(acceleration or heavy loads) you will get more power and better fuel economy with high octane fuel...once again, ONLY if your car was designed to use and benefit from the higher octane rating.

 

^^^^ basically what he sayz

Im using whatever highest the petrol station can offer on my c230
mostly 97 RONs

 

When I bought the car last week, the dealer told me that mid-grade fuel was fine. He said that once a month, fill the tank with 91-92 octane.

 

Sounds like a bunch of old wives tale crap. The uninformed always assumed or had been incorrectly told that "premium" gas had additives that were simply better for the car and the story line seems to makes sense to the uninformed. Problem is, it is simply not true. If you use lower octane fuel, your car'd knock sensors will help insure self preservation, but you will lose power and fuel economy in high load situations due to the timing being retarded.
I would always advise using the octane recommended for any particular vehicle. The only exception is older cars with lots of carbon build up may benefit from higher octane. The carbon build up can hold heat and pre detonate the fuel. Not something any W204 owners would have to worry about yet.

 

I only use 97 octane on my car. Nothing less. If I wanted a car where I could scrimp on fuel, I would have just bought a Toyota. haha

 

I am starting to get the feeling that you could not possibly be an actual human being . . .

 

And you're actually listening to a dealer? They are notoriously misinformed.

 

C300 engine has very high compression ratio, 11.3:1. So, I would use 91 all the time.
FYI, C350 engine has 10.7:1 compression ratio.

 

It should not be a big problem...

1) There are knock sensors!
2) Even high performance manufacturer like Porsche says it is okay to run on "regular"/87. However, it will degrade the performance!
3) Some countries don't even have premium fuel...


If you really want to try it, run your car close to empty. Put $10 and drive around the gas-station, if knocks and the car runs like crap, fill the rest with premium again!

C250 has a high compression at 11.4:1! It is higher than C300/C350/C63...

 

I use 93 octane, I don't think I've ever seen 97 before though.

 

in the states, you'd be hard pressed to find anything higher than 93. California usually only has 91 octane as the highest, but I know other states have 93. There is actually 1 gas station in northern cali and has race octane fuel, I think its 100 octane. haha

 

I understand knock sensor thing.

My point was, with this kind of compression ratio, engine timing will be definitely retarded, if lower octane gas is filled. Consequently, you will have less powerful/responsive car with lower gas mileage. It's just not worth it.
My other point was, sometimes, it could be a marketing thing asking for premium gas (so that people feel they are driving a premium car). With this level of compression ratio, possible marketing trick is ruled out. It means it's a real requirement for the car to perform the best.

 

My last 2 vehicles were BMW's and they both required and were given nothing less than 92 octane. When I first started looking at MB, I assumed that the same was true. (premium 92 or better fuel). I always was and I am now prepared to use premium. However, as I said the dealer gave me a different story. This made me think that maybe MB vehicles are capable of using various types of fuel without harm to the engine. The manual says to use 91 octane. Many here are debating this. Who is right????? I am going to do what the manual states and be satisfied that it would not be in the manual if MB engineers believed different.

 

Just think of it as gas for cars is equal to food for people. If you eat junk food, you might not die but you will not perform at your best and may even be causing some damage as you go. If you eat properly, you perform better and likely are leaving no damage behind...unless you get a lemon...and then I guess you are pretty well screwed...

 

Listen, your not going to "damage your engine" by not using 91 or premium octane fuels. But your engine will not perform at the optimal timing and power if you choose not to use premium octane fuels. The engine will automatically sense the additional knock due to the lack of octane in the fuel mix and adjust the timing accordingly.

Personally I don't feel it is worth it to use 87 octane, or anything lower that 91 for that matter. Not only do you lose HP and thereby power, this wastes more gas which eats away at the fuel cost savings. Additionally, it also can cause some eratic behavior when it comes to stopping when you use 87 octane, even after you come to a complete stop, it can sometime lurch forward as the engine has adjusted timing, but tranny still shifts down at the same rpm's. (dangerous in parking lots)

Bottom line is this: Use 91 octane unless you are really tight on cash or if 91 octane is not available, in the short run it will not damage your engine, but could pose other threats (lurching) and will not really save you much cash. In the long run (multiple years) it could cause excessive wear to an engine or excessive gunk build-up. But on to my most important point:

**If you are constantly using 91 octane from the same gas company (such as shell V-Power) you will be doing the same, if not more damage then commonly using 87 octane.**

With all the additives in modern gasolines, much like the bacterial resistance problem, the additives get rid of most of the engine sludge and gunk and protect from most problems, but not all of them. And over time, the types of "waste" or by-product that is not eliminated by the particular additive(s) will build up and cause problems (even the additives themselves can build-up). So the best thing to do is this:

Whether you use 91, 89, 87, or some other octane fuel, I recommend to switch between 2-3 major gas retailers (so that you don't mistakenly get fuel mix with the same additives). To be sure of this you can use 3 major competing gas chains. I use BP 91 octane, Shell 91 octane (v-Power), and Mobil/Exxon 91 octane. These three gasoline companies all use different additives in their fuel. I use each brand for around 3,000 miles, and then switch. This way it eliminates virtually any type of build-up from occurring. If you are so inclined, you can choose to always get gas at Costco or Bj's if available, as they fill up their storage tanks with the cheapest gasoline brand that day, and then you also get fuel savings; so you get to have your cake and eat it too!

If you happened to read this far, I hope I was helpful! Thanks for reading, haha.

 

Ditto...You will save NO money and it's worse for your engine.

 

Good analogy....point taken!!!! Thanks!!!!!!