i got the 3.2 liter engine so 21 mpg is all i could get. It's brutal in the city though, sometimes i would see 15 mpg

 

Damn! Something must be wrong. My E55 gets 20/16mpg

 

really?

I got a C240 loaner car recently and it also averaged 21 mpg, so i thought i was doing well getting 21 mpg on a c320

 

I get about 21 with the 3.2 with an average speed of around 30mph. That's with the AC running.

 

I haven't reset the computer since I got my C240. In 12,000 miles of driving, mostly around town and really short trips to work (3 miles) I have averaged 21 mpg. And I live in Florida so the AC is running all the time. I always run Chevron premium (93 octane).

GGM

 

Its not about peak efficiency for normal driving. And for everyday driving, you shouldn't be running the engine hard enough for it to matter. It takes so little HP to keep the car moving. And at partial throttle, I'd bet the car makes no less HP than with premium.

Tell you what, I'll challenge you to a tank of low octane fuel, you in your E55, me in my lowly supercharged Coupe. In normal driving, i don't think you'd loose any mpg.

 

You are not seeing the entire picture. Very little HP is needed to keep the car moving but how often are you at a steady state, flat cruise? Part throttle is a very key place where higher octane is needed. Load is still fairly high and A/F ratios are very lean. Part throttle knock is the most common occurance in a street engine.

In simple terms, if the ECU reduces output at a given RPM, you need more RPM to create the same HP. More RPM equals more fuel.

I have run all my cars on various octane rated fuels and the only one that does not result in a statisitcal increase in MPG is the Denali. The E55 now has a Powerchip with 93 octane tuning. The numbers on the CLK and Denali are stock. The 93 octane was a mix of Union 76 91 octane and 100 octane. The 94 octane is what I have in my tank on the lake. Even though most boats claim to be 87 rated, most of them run so much better on the high test. My modified SeaDoos absolutely need it. EGT goes crazy if I run 91.

Here are my notes from both Benzes (commuting 21 miles each direction) and the Deanli (lake house to home 60 miles of mountains and 100 miles of freeway). Some of these numbers are averages from a few tanks but none were more that a tenth or two off.

E55 pre chip - 89 octane 16.4 mpg
E55 pre chip - 91 octane 17.7 mpg
E55 post chip - 91 octane 17.1 mpg
E55 post chip - 93 octane 18.1 mpg

CLK430 - 89 octane 15.8
CLK430 - 91 octane 16.4

Denali - 87 octane 14.7
Denali - 89 octane 14.8
Denali - 94 octane 14.8

When I was building engines for people, this is one way I would determine the correct octane rated fuel for their application. When MPG stops increasing as octane increases, this is the right fuel. Without going back to my notes, I'd say that 90% of the vehicles I tested this way in 20 years showed a statistical change in MPG when octane was lowered.

 

From the perspective of working as an engineer for Amoco Oil Co for seventeen years I would not suggest using regular grade gasoline in anything other than your lawn mower.

We used to "cut in" "interface" into regular gasoline batches. Sure it was still 99% good-ol gasoline but there was also a component that was anything from #2 heating oil, jet fuel or even water that got into a sump tank.

 

i have lead foot...only around 16-17mpg on avg for me.

 

I did a search but couldn't find anything ..... just wondering if there was any performance advantage to using higher than 91 octane in a c230k. Anyone know if the computer will take advantage of better gas (i.e. raise boost level or advance timing or ???)?

 

are you talking higher then 91 as in 92,93? or like racing fuel?

 

No performance advantage at all, tried Unocal unleaded 100 octane, no difference on dyno, no difference in feel.

 

STFF with someting like "octane booster". there was a thread on here not too long ago with regards to octane booster / higher octane gas. A LOT of people had first hand experiences with no advantages at all.

 

I heard that octane boosters are used in the summer months.

Theres really no difference in "feel" with octane boosters.


but theres a diff if I use 88octane fuel rather than the usualy 93

 

no

 

The only way you can benefit from using a higher octane fuel (101, 104+) is if your ECU is modified. Modified meaning it's been programmed for more aggresive and more advanced timing. IF it is then yes you'll benefit from it. I have a custom ecu i'm using and will never go back on pump. Mine runs strictly on 104 and it is a noticeable difference.

 

Buellwinkle hit the nail on the nose - I now have 95 & 100 octanes available from the pump locally. It's proportionally more expensive than the 91 octane of course, so I would only use it if there was a performance advantage. If Buellwinkle dyno'd with different octanes and says no difference, thats pretty definitive to me. Thanks to all!!

 

Does that mean that I can use lower octane gas without any disadvantage? I guess not..

 

FYI:
MBWorld thread: Shell V-Power New Formula_100 Oktan

 

bnzct - wow ... I even posted in that thread!!! How short lived a memory can be.....

JamE55 - are you running a stand alone ECU, or did you have your stock ECU reprogrammed (or chipped)?

 

Custom programmed ECU.

 

If this has been beaten to death already, I sincerely apologize. I did do some searches and never found an answer to my question "can my 06 C230 Sport (no kompressor) run 89 octane E10 and if so, what do you think are the shortcomings". Gas here in Hawaii is starting to go up again (like everywhere else) and was wondering if going to the next lower octane would be ok and what would the trade-off(s) be. Thanks in advance!

 

there is lots of discussion about octane here.

https://mbworld.org/forums/showthrea...ghlight=octane

 

Gas is still very cheap in the US and you also have reasonable pricing on premium running about 8-10cents more per gallon.

Here in Canada (let me remind you we are a net producer of oil) our gas is priced at $1.04/litre regular and $1.15/litre for premium. The 11 cents spread to get premium is the killer as 4 litres = 1 US gallon so that is a premium of 44cents per gallon.

Some how the math got mixed up north of the 49th

 

try 110 for regular 121 for premium...damn taxes