[leetec]

Hi everyone I was reading an article on the web and it stated that premium gas only cars can run on regular gas. you'll just lose on perfomance. The knock sensor will handle everything else. Is this true can I get a conformation? Reason is of course everyone knows the price of Premium gas in CA is crazy $4.59 per gallon and climbing

 

[ohlord]

The

caveat
you'll just lose on performance.

these are 7-10 year old engines high compression and without the current days engines sensors.Read the manual about keeping speeds down and full throttle loads up hills,etc..
take your chances for people in denver or other high alt cities 89 will pass.Try it if you want the worst that can happen is a burnt piston or three
ohlord
knock sensors have come a long way in the last 7 years.

 

[Check Codes]

If you do a search you will find lots of threads on this topic and always tied to an increase in gas prices. What will you do at 6 bucks, mix in water? The sinple fact is that this is a high compression ULEV performance engine DESIGNED for premium fuel. Can you run regular in a funny car? NO! Knock sensors cannot compensate that much, period.
I've said it before and please don't take it personally, but you are applying a Ford mentality to a Mercedes and if you want to apply a Ford mentality then sell the benz and buy a Ford. The damage you do will end up costing you lots more than the couple bucks you'll save on a fillup.
But if you want to apply generic information then all I can say is take care and enjoy ruining the ride...

 

[leetec]

well here's the link to the article

http://www.nytimes.com/2008/08/03/automobiles/03OCTANE.html?no_interstitial


Motoring - Premium Gasoline Required? Not Necessarily - NYTimes.com

 

[meooem1]

just picking brains here! how does the lower octane gas effect our engines? is it the cats or can it damage the engine. i personally have always used premiem, but what is the possible damage?

 

[ohlord]

Somone is

pointing out a ny times article and they are not paying for your engine.
Mercedes did not scale this high compression engine to regular fuel.The engine management systems used now are quicker to respond to knock and detonation.
lower octane takes a lower level of compression before it ignites without the presence of a spark,just like a diesel.High compression engines develope much more compression of the air fuel mixture and require the extra delay of premium so the spark plug or plugs can ignite the mixture at the best time.
octane fuel to delay the firing until the stroke of the piston reaches the optimal point.Low octane will allow that to happen before the proper position in that cycle,slamming the piston down the bore when it is still trying to reach the arc of the crankshaft that it needs to be at to go on the down stroke,not a good thing.I will takes my chances with other forms of gambling
ohlord:bowdown:

 

[Check Codes]

"Not necessarily" are the KEY words here.

That is an article written to the masses, and "the masses" DO NOT include MB owners (or Porsche, BMW, several others).

Most cars are designed to utilize premium fuel and those are okay on whatever pump octane you dump in. However, some cars are designed TO USE, not utilize, premium. In other words, the basic engine configuration REQUIRES a certain octane rating to perform nominally, not just optimally. The electronics that are hung on the engine don't "adapt" it to run on other octane and will do their best to compensate if you abuse the car by doing so, but they cannot rectify the underlying issue of the low octane because the static timing, combustion chamber and compression ratio are ALL geared towards the specified octane number. PERIOD.

So...running improper octane gas will save you about $3 on a tank of gas assuming an average fillup of 15 gallons, so $65 instead of $68 for example. If you fill up every week that saves you $156 a year, although you will fill up a bit more often because you won't get the same fuel economy. But I'll let you have the full $156 figure.

The cost of a pair of aftermarket cats welded in is about $300; OEM figure a grand a side. O2 sensors are $300-$800 a set depending on whether you buy universals and install them yourself. An EGR valve is a couple hours work and $140. Plugs aren't terribly expensive, but if you pay to change them they sure are. Cleaning up a combustion chamber could also be costly. All of these things are within the realm of possible damage by running improper octane fuel that as a result does not burn properly.

Is any of that worth $156 a year (which, coincidentally, won't even pay for your NYT subscription)?

So if you're going to dump regular gas in your engine, be sure to set aside the savings to pay for the added repairs you will incur (unless you first dump your car on some other unsuspecting soul). It likely won't pay for all of the repairs, so set aside some extra money for that, too.

Take care and enjoy the ride,
Greg

 

[ozcan]

Well explained Ohlord I would not risk the engine with low octane gas. There were times I had to mix 89 octane with my remaining 93 octane in the tank. But just enough to drive to next station to fill proper octane.

 

[lkchris]

If you use regular fuel in your Mercedes please post your VIN number here so we can avoid your car when it comes up for resale.

 

[Kajtek1]

I was filling up premium to my Volvo even when 20 cents price difference made 25%.
Driving often in the mountains I even used Premium in cars design for Regular. With premium struggling on steep slopes the car didn't have to downshift, giving not only much better performance but also fuel savings.

 

[Check Codes]

I was filling up premium to my Volvo even when 20 cents price difference made 25%.
Driving often in the mountains I even used Premium in cars design for Regular. With premium struggling on steep slopes the car didn't have to downshift, giving not only much better performance but also fuel savings.

Kajtek1, you make an excellent point. Back when gas was $1.50 a gallon it arguably made more sense to try and "skimp/save" by running regular instead of premium since the percentage increase was roughly 13-14% of the bill. Now that gas is three times that much, the cost savings is minimal.

Indeed, for those with adaptive cars that can recognize and adapt to higher octane (but don't require it), the improvement in fuel economy might in reality make premium a smarter buy for such folks.

Another way to look at this: you save $3 on a tankful of gas, which equates to roughly 20 miles of driving. By watching how you drive and keeping your tires properly inflated (and your car otherwise maintained) you can save more than that through increased fuel economy.

Or you can cut out one latte a week.

Take care and enjoy the ride,
Greg

 

[ozcan]

So, in short we need to s t i c k to the recommended octane which is premium.

 

[mlfun]

Here ya go

USATODAY.com - Why use premium gas when regular will do?

All Porsche engines are designed for premium, too, but it's not available everywhere. "Our cars must be able to drive all over the world, and so we are able to run on regular," says Jakob Neusser, director of powertrain development at Porsche's research and development center in Weissach, Germany. "You don't have to feel that a mechanical problem or anything else will happen" using regular gas, even in the highest-performance, regular-production Porsches.

So, in short we need to s t i c k to the recommended octane which is premium.

 

[steve e class limo]

Our standard RON over here is 95 and costs $6.43 per us gallon . We can also get E 5 , 95 % petrol and 5% bio , it has a RON of 99 and costs the same about $6.43

 

[Check Codes]

Here ya go

USATODAY.com - Why use premium gas when regular will do?

Correction: Here ya DON'T go.

You can find articles on anything, including "proof" that the CIA blew up the WTC towers.

It is almost always dangerous to apply general principles to specific situations.

You can do whatever you want to your car, but suggesting the same to others is foolhardy. You going to be paying for their repairs? Not a chance, and neither is the NYT or USA Today.

Here's the other half of the article that is left out: Why use regular gas when it WON'T do?

 

[mlfun]

Here ya go (2). See a pattern ?
---------------------------------
On the one hand, we have our BW experts.
On the other, here is a relevant article from PopMech.

13 Must-Know Tricks to Max Out Your Road-Trip MPGs - Popular Mechanics

 

[Kajtek1]

Besides having Premium and Regular we do have in US gasoline and the stuff they sell in California. I am not even talking about 98 octanes available in other countries. The watery stuff sold in California is one of the reasons why I decided to buy diesels.
At least I don't have the problems you guys do
Our only gasser -ML55AMG will be running on Premium. I think our son do the same in his ML320

 

[Matt L]

The problem is that the knock sensor cannot handle everything.

Premium resists preignition, meaning that the edge gasses resist spontaneous combustion by pressure alone, before being hit by the flame front.

There are several ways that engines can reduce the pressure, but it does come down to lowering the power output.

If you reduce the pressure by delaying the spark (which used to be the only method), you increase the heat at your exhaust valves. A full-throttle run could cause you to lose a valve.

A better method would be to alter the camshaft timing to reduce the maximum cylinder pressure. But this will also result in reduced engine efficiency.

The best method would be to alter the combustion chamber size, directly affecting the compression ratio. I do not know of any modern engines with this capability.

 

[Check Codes]

Here ya go (2). See a pattern ?
---------------------------------
On the one hand, we have our BW experts.
On the other, here is a relevant article from PopMech.

13 Must-Know Tricks to Max Out Your Road-Trip MPGs - Popular Mechanics

Again, applying general principles to specifics is not always the best way to proceed.

And again, if you want to experiment with your own car, you can also buy really cheap oil (or never change it at all), buy your generic brake pads at Kragen and put in dot 3 brake fluid, all while never changing the AT fluid or coolant, either. And Pep boys is running their "buy three get one free" tire sale, too (load ratings are meaningless anyway). But...suggesting others follow such poor examples is really, really bad form.

Take care and enjoy the ride,
Greg

 

[Check Codes]

The problem is that the knock sensor cannot handle everything.

Premium resists preignition, meaning that the edge gasses resist spontaneous combustion by pressure alone, before being hit by the flame front.

There are several ways that engines can reduce the pressure, but it does come down to lowering the power output.

If you reduce the pressure by delaying the spark (which used to be the only method), you increase the heat at your exhaust valves. A full-throttle run could cause you to lose a valve.

A better method would be to alter the camshaft timing to reduce the maximum cylinder pressure. But this will also result in reduced engine efficiency.

The best method would be to alter the combustion chamber size, directly affecting the compression ratio. I do not know of any modern engines with this capability.

Matt L, your comment about varying combustion chamber size reminded me of the old Honda CVCC engine with the (kind of) dual chamber setup. Worked really well -- until it didn't.

And actually, the real problem is not engine design, knock sensors or anything else related to the car. Rather, the real problem is human: some people will buy a silk purse and treat it like a sow's ear. Such nonsense is also referred to as penny-wise and pound foolish (or actually, perhaps it's just plain foolishness). There are lots of ways one can choose to save money, and not all of them require abusing your vehicle. So why people choose that one is beyond me.

Take care and enjoy the ride,
Greg