Check Engine Light: 6 CODES!!!!!!!!!!!
02-15-2011, 07:03 AM
#77
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Join Date: Dec 2003
Location: Vancouver, BC, Canada
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2003 C230K Coupe Orion Blue
When you actually compare the cost of 100 miles with 93 octane vs. cost of 100 miles with 87 octane, it comes out about the same. Let me explain. The above is true because the MPG you'd get when you use 93 octane is about 2 to 3 MPG more than if you were to use 87 octane. When you use 87 octane knock sensor will detect the engine knocking and the ECU will retard the timing accordingly - as a result, fuel efficiency goes down. You will not 'hear' anything unusual because the knock sensor is doing it's job.
Summary - people think they are saving money by pouring 87 gas in to a car that REQUIRES [by the manufacturer] 93 octane gas due to high compression ratio. In the long run, you are actually ruining the engine. This is NOT a debate. If you'd like to pour 83 octane (or kerosene) in your MB engine, please continue. :-)
Summary - people think they are saving money by pouring 87 gas in to a car that REQUIRES [by the manufacturer] 93 octane gas due to high compression ratio. In the long run, you are actually ruining the engine. This is NOT a debate. If you'd like to pour 83 octane (or kerosene) in your MB engine, please continue. :-)
So I'm not trying to rain on your parade, but imo the "regular gives you less mileage than premium" is bunk. With that said, I'm not condoning running your car off 87.
The cars CAN run in 87, if you check your manual. It just states not to race your engine or go past 2/3 throttle iirc. Here in North America (though it's getting increasingly rare) not every place out there will have 91, if you're out in the sticks. I'd imagine that all production cars here MUST run off 87 without blowing up by law.
Lastly, why is everyone saying 93? Maybe in Canada it's different, but over here my manual says 91. Only 1 company that I know of (Chevron) sells 94 around here, and only riceboys driving Skylines and Civic Type Rs (okay, maybe the occasional Lambo too) use it.
Last edited by slammer111; 02-15-2011 at 07:12 AM.
02-15-2011, 07:35 AM
#78
Super Moderator
Standard off the showroom floor these cars run a very mild timing advance map because Benz know that around the world they will have crap gas put in them & want no trouble. If they do knock the ECU will immediately retard the timing at the onset of that knock & you will end up running retarded most of the time. Not ideal for efficiency. The Star allows one to select higher octane setting to use a more aggressive map. If you set up to run on higher octane then you must use that. When doing one of my octane lectures on the W204 forum a Benz programmer came on the thread & confirmed my comments.
The M272 quad cam engine has far more efficient breathing than earlier designs & a high CR. Running it on low octane gas makes no sense. At the same time if you were in Europe you would select 95 RON Eurograde. No need to run 98 RON because you would have octane giveaway. Running higher octane than required is also a waste of time unless the fuel happens to be more dense = higher energy value.
The answer for max efficiency is to run what the engine was designed to run on as Johnand says.
You will not blow up an engine as long as the knock detecting programme can retard the timing sufficiently - However knock, pinging, precombustion, detonation by whatever name you know it can be very destructive.
As engines get older & foul themselves a little their octane requirement will rise.
You will never achieve optimum fuel consumption running with retarded timing - easily proved on a decent dyno with controlled IAT etc.
The M272 quad cam engine has far more efficient breathing than earlier designs & a high CR. Running it on low octane gas makes no sense. At the same time if you were in Europe you would select 95 RON Eurograde. No need to run 98 RON because you would have octane giveaway. Running higher octane than required is also a waste of time unless the fuel happens to be more dense = higher energy value.
The answer for max efficiency is to run what the engine was designed to run on as Johnand says.
You will not blow up an engine as long as the knock detecting programme can retard the timing sufficiently - However knock, pinging, precombustion, detonation by whatever name you know it can be very destructive.
As engines get older & foul themselves a little their octane requirement will rise.
You will never achieve optimum fuel consumption running with retarded timing - easily proved on a decent dyno with controlled IAT etc.
02-15-2011, 08:07 AM
#79
MBWorld Fanatic!
Great info, Glyn, as usual. I use 93 because no stations around here have 91. I just get frustrated at the attempts to tie 87 octane fuel to unrelated problems, like the cam magnets. It's overboard.
