Hi,

I have a new C230K Sport Sedan. I do 10 miles everyday in the city (a lot of stops and accelerating). Fuel consumption is extreme compared to what manual says. It is 16 mpg (15 lt/100km). The manual says that the city mpg should be 24 mpg (10 lt/100km). Is this normal? I use 93 octane BP.

Thanks,
Kaan

 

The EPA mileage estimates aren't worth a whole lot, especially the city estimate.
Actual city mileage will depend heavily on your driving style during the "stops and accelerating" and what you have in the car (weight). There are also smaller but measurable effects from tire air pressure, tune ups, etc.

Does your car come close to the EPA estimate for highway mileage?

Does your manual recommend 93 octane gas? If not, you're wasting a whole lot of money and gaining no benefit from using it. Actually, your car's engine will perform better on regular grade gas if it doesn't "ping" under load.

 

Lugnut, your right on I use Vpower 93 octane by Shell and my gas mileage and performance have increased. I own a 99 C280. But to the original post, driving round trips of 10 miles a day, is probably the worse type of driving for mileage and the engine also. I would at least and you have the time, take a nice ride on your day off and put about 100 miles on the car at the top end of the speed limit, if you have the 5 speed auto, drop the tranny to 4, this is the sport setting, it will increase the RPM about 500 RPM and the engine will run a little warmer, which will burn off the carbon deposit building up inside. Also, when you do this fill the tank with 93 octane of the highest you can get you your area, Mercedes designs their CPU to take advantage of higher octane fuel, not like American manufactuers, who don't. Believe me and lugnut, the higher the octane the better you Benz will run. Avoid additives or octane boost they sell in parts stores. The only thing I would recommend in that area is a professional fuel injector cleaning. In your case about one a year is good. Take a long handled screw driver and hold it up to the fuel injectors if each one is clicking steadily then they are OK.

 

the c230 requires at least 91 cotane

 

You misunderstood me. I'm saying the lower the octane rating is, the better the engine will perform, provided it doesn't ping. Regular grade gas is more combustible than premium and more desirable, not to mention cheaper. I don't believe you understand the principle behind higher octane gas.

The only reason you want to use premium is because your engine runs too hot to run regular and pre-ignites the gas before the spark plug lights. These are primarily high-performance engines. Premium grade is NOT so combustible that it will cause pre-ignition (or pinging). It burns slower than regular grade gas.

It makes absolutely no sense for MB or any other manufacturer to program for premium grade fuel if it's not needed to prevent pinging. There's just nothing to take advantage of. Where are you getting this misinformation?

 

If available try some Shell Vpower 93 octane or Sonoco 92, fill the tank and then go for a nice long ride and see if mileage and performance improves.

 

I've gotten into this conversation before, and you correct about the difference between octanes and how they really work.

However, in my owners manual if says very plainly, using a higher octane gasoline then the 91 recommeded will improve performance and mileage. I did some checking and consulted with some very knowledgeable folks, one a auto engineer I went to HS with. All had the same opinion, the Mercedes statement is quite true and it is possible to program a cars CPU to higher octane and improve performance. On the other hand my daughter owns a 01 Dodge Neon and the recommended octane is 87, the owner's manual goes on to say 89 can be used if 87 is not available, but should only be used in an emergency. It also states using gasoline higher then 89 octane can damage the engine and is not recommended and will void the warranty.

So, what can I tell you, the age old octane question, Yes or No!

 

it's true under the "igntion parameter" adaptation.

the control unit change the igtinion time.

 

I also have some stalling problems with the car. In the morning when the engine is cold the car stalls at low rpms. It does not lose power but spudders (shakes terribly) unless you push the pedal and take it to higher rpms. Can this be from the 93 octane BP that I am using?

Thanks,

 

Yes, it's possible to advance the ignition timing and lean out the air/fuel mix through the CPU. That doesn't mean it should be done for all engines or that there is an advantage to doing it. It doesn't matter if it's a MB or not. Not all MB engines are high performance engines. You can buy aftermarket CPU tuning that does this, but 99.99% of the time it's ineffective on a stock engine and decreases performance. Why do you suppose that is, if MB already does it as you claim?

What you don't seem to understand is that it isn't necessary when the compression ratio is low enough to allow a more streetable ignition timing and a safer air/fuel mix. There's nothing magical or mysterious about premium grade gas. Don't use premium to gain performance. It won't happen. Premium will help your engine from losing performance, if it does not perform efficiently with regular. What you're doing is preventing a loss of performance. There is no gain.

MB and other manufacturers are concerned with reliability and durability. You lose both when you advance ignition timing and lean out the air/fuel mix. You also lose gas mileage and cause more pollution. Performance will decrease if the gas you buy isn't prefect as the CPU tunes down to compensate for the engines inability to operate efficiently with a high performance tune and less than perfect gas.

I'm not saying MB doesn't do performance tuning at all. I am saying they don't do this to all of their engines. It's not smart engineering and MB engineers aren't dumb. All internal combustion, street-legal car engines operate by the same principles. There are no magicians at MB.

BTW-If your manual says to use 91 octane then you should use premium grade gas. So, if you used regular grade gas then you goofed and yep, your engine performs better with premium. If you use regular, the CPU will retard the ignition timing to prevent pinging. This protects your engine at the expense of performance.