pointman

If are gonna be cheap about buying premium gas, you shouldn't have bought a Mercedes, let alone an AMG. Its unfortunate that used C32's are going for so cheap now.

zcct04

Lotsa posturing here and not much factual guidance. My daily driver was a supercharged pontiac. It had a knock sensor that retarded the timing when it heard first indications of detonation. This allowed use of lower octane fuel but at a penalty in performance. The knock sensor worked well and effectively prevented any long term engine damage, even if you were routinely running dung gas. The Pontiac community got pretty good at diagnosing the amount of KR (knock retard) that different mods could create, because some combinations of breathing restrictions coupled with a smaller supercharger pulley could actually make the car run slower.

Does the C32 have a knock sensor? Does it retard timing? Do we know how much?

sdsilverm3

It doesn't matter if the C32 has a knock sensor or not. The fact is that running "regular unleaded" in a car the REQUIRES premium is a dumb thing to do. Yeah sure the computer will retard timing (that should answer your knock sensor question) but what happens when you run on retarded timing???? Motor runs hotter and is less efficient.

Why did one buy an AMG if they cannot afford the extra $0.20/gallon? What factual guidance do you want ????

sanf

if u not planning on keeping the ride. just throw in whatever runs and sell the ride in a few years. (and make sure that no one from this forum buys it)

HLG600

Ran regular on a 2003 ML350 for 3 years: no problems whatsoever.
Ran regular on a 2003 S430 for about a year: same deal.

Both these cars require premium, yet ran fine with regular. Why, because they're relatively simple naturally aspirated motors with moderate displacement. On more complex motors, stick with premium. Since the SL has a great deal more components to the motor, I run only premium in it. Since your motor is supercharged, you should only run premium in it.

MarcusF

Yes the C32 (as well as a ton of other cars) has knock sensors. Have any idea how the system works? I do. When the ECU determines the engine is knocking, it retards the timing. The ECU doesn't retard it a little, it retards the timing to "this engine can’t possibly ping down here" levels - and then it gradually brings the timing back up until it sees a knock again. This procedure repeats itself until the car stops pinging (when that low grade sludge in the tank is used up). The point is, the ECU retarded the timing when it saw the first PING, and then every subsequent PING. That means the engine is PINGING.

You say there is no long term damage. I say, I’ve rebuilt plenty of engines and know that to be incorrect. Want to blow a head gasket in half the time it would normally take? Looking forward to replacing a set of valve guides? Just run regular gas. Why? Aside from lousy fuel economy and no power, engines with retarded timing have dramatically higher combustion chamber temperatures. Anyone whose ever looked at an EGT gauge or looked at a cylinder head temperature gauge (this is where the thermometer screws into the head and checks the temperature of the aluminum not the coolant) can immediately tell that the combustion chamber is much hotter. And a blown head gasket is the least of the problems. I’ve seen holed pistons from pinging. Will it happen on the first tank? Nope. The second? Probably not, but when the headgasket blows, the engine starts sucking oil past those worn guides, or the engine limps into the shop on 5 cylinders, you'll realize that the Mercedes-Benz powertrain engineer with the PhD in Mechanical Engineering who designed the engine just might be right - it does require premium fuel.

Now, assuming someone saves a whole $3 per tank using substandard fuel (15 gallons at 20 cents per gallon savings), how many tanks will it take to break even on a valve job?

sloanben

Still mostly speculation and opinions here. I guess nobody has tried the experiment in question so no facts are available. I'm not surprised given the mindset of folks who tend to buy these cars. There seems to be a fair amount of pride in driving a car which requires premium fuel!

Thanks anyhow.

sdsilverm3

Speculation and opinions??

You go ahead and experiment because the answer to your question is common sense. If your car is under warranty the FIRST thing the dealer will do is check to see if you are in fact running the correct gas. If you're not, bye bye warranty. That is a FACT.

What MarcusF replied with is FACT. Do you think manufacturers require PREMIUM gas on high performance forced induction and high compression motors for fun?????

Please go do some research regarding combustion engines and why higher octane gasoline is REQUIRED (not recommended) before you mouth off about what is/isn't fact.

zcct04

True confessions: I almost always ran premium. Sometimes stepped down to mid grade when the prices were screaming up. Never had the courage to run regular because I just wasn't sure. And I didn't have any FACTS on which to base that decision. And FACTS is what we're looking for here.

"the FIRST thing the dealer will do is check to see if you are in fact running the correct gas. If you're not, bye bye warranty. That is a FACT."

Can't resist stirring the pot. How many dealers really have fuel testing equipment and knowledge to test the octane of your gasoline?

ScottW911

Dude, you just don't get it. Yes, MarcusF presented some pretty strong facts, based on repeated observations (I believe that is the basis of scientific study). No, it is not speculation. I have not heard anyone expressing "pride in driving a car which requires premium". It Sucks to pay that much for gas!

It appears that the only "speculation" is your level of expertise, compared to guys with years of tuning, driving and racing the C32 and C55. My "opinion" is that you should go ahead with your "regular gas" experiment and report back to us in a year or so.

Bah-bye.

sdsilverm3

Sure let's stir the pot.

There are other methods other than an octane tester to determine the problem at hand. They don't need to be fuel experts to know what happens to a motor when it is damaged due to excessive detonation and the result of running fuel that is not within the recommendations of the manfuacturer.

So let's keep stirring.....

What else causes a motor to excessively detonate when the car has not been at all modified to increase the pressure inside the cylinder walls?

If we're talking about a complete motor replacement because it was destroyed from detonation, you can probably bet someone other than your everyday tech will look into the issue.

Now, since we're all "posturing", who is willing to test the theory out. Run your car on Regular as hard as one would with Premium and report back in a year or two. Since you all want FACTS, someone should go do it and provide us with some.

I can tell you from experience, that even WITH PREMIUM, my car will ping in high load, low RPM situations. I wouldn't even bother with Regular gas.

sick430

Here are some facts for you my friend drives a clk 320 and was running 87 in it for app. 6-8 months, we both drive our cars very hard. He was complaning ygat his car was running like ****! I told him he neefs to change to 91, in the time he ran 87 I think 3 sensors went bad. After switching to 91 car is running much better and stronger!

sloanben

I poked around on the internet and did find some information. The suggestions that the engine runs hotter, performance may be degraded and that supercharged engines are the least adaptable to lower octanes are supported. Notions about engine damage and warranty problems are not supported.

You all might appreciate this news article, which features comments from MB-USA and from some Chevron fuel engineers:
http://www.toyota-4runner.org/showth...p?threadid=683

Thanks!

flush

"Actually, the price debate is nearly worthless. At 20 cents more for premium, pumping 20 gallons of it instead of regular would cost $4 more. Annually, that's a difference of $171 for a vehicle that averages 14 miles per gallon — as some big sport-utility vehicles do — and is driven 12,000 miles a year."

Great link!

This begs the question. Is anyone going to quibble over $171 per year? If you do, then you have more pressing issues than owning a car (any car).

pointman

You love Nascar don't you.

Carl Lassiter

Do you mean 535d?

One of the major benefits with diesels is that they have a far greater range than their petrol equivalent. 500 miles between fill ups makes everyones life easier.

To the OP- 20 cents difference. Come on now

Rod Spohn

Sorry guys I drive an old S class but am enjoying this thread. I also have a question. Out by the raceway they sell 101+ octain that I've seen. Also at Lake Havasue they sell it for boats. I have toyed with the Idea of running a tank through to see what it would do both proformance wise & cleaning out the engine. So good idea or bad to run that fuel?

Fifth Ring

I tried 103 octane at the track and honestly I could not tell any difference in performance. Bummer since it was like $4 /gallon. I also don't think that there is any "cleaning" associated with higher octane.

Higher octane means more resistance to pre-detonation or pinging, and it allows you to run higher compression. But since compression is what it is, at some point the higher octane does not help. In a computerized engine, higher octane might eliminate pinging under extreme loads, which will stop the computer from retarding ignition, so you can increase performance. But at some point, the octane is high enough to eliminate all pinging, and more octane will do nothing.

Carl Lassiter

https://mbworld.org/forums/w211-amg/197529-new-e63-w-030-perf-pkg-w-pics.html

This thread is ongoing in the W211 AMG forum and relevant to what we're talking about here.

FrankW

was it a 540i vs a 535d? forgot. have to dig up the episode, but can't remember which was it.

Carl Lassiter

I never actually saw the episode in question. I just know there was a 740d but never a 550d or 750d.

My father back in Europe has a new 535d Sport Touring (engine is a 3literTT, despite the misleading badging). 284bhp, 429lb/ft and still delivers a real world 33mpg. 0-60 in 5.8, ltd to 155 and a dog cage in the back.

He traded from his 2004 17mpg Range Rover so needless to say he's pretty pleased as that thing cost $160 bucks each fill up.

Great looking C32, btw. I've always have a soft spot for that car ever since my aforementioned father bought one in 2003. They still have it and continue to blow the doors off any uninformed 330i's.

FrankW

I remember it was an 06 episode, so it may have been the 545i vs 535d E60 with the M-tech packages.

btw, if your dad wants a set of 22x9.5 custom forged wheels let me know I have a new set that I need to sell. they're the DCR Laguna Seca in gloss black.

Carl Lassiter

I'm sure they're great but it's the mother's DD so she likes the stock 17s and the car is briliant silver so wouldn't suit the rims like obsidian. He wants to get an E63 for her but she is as in love with the C32 as the day she got it so is so far resisiting.

I'll try and find the episode, sounds interesting.

FrankW

check out finalgear.com if you want to download the Top Gear or Fifth Gear episodes if you use BT.

deltadude388

It's not about pride, you mean to say you are smarter than all the engineers at MB?? End of the day, it's your car, I think most people here careless if you run it on water.....