Which is better gas to fill your car up with--Premium or Super? - Page 2 - Mercedes-Benz Forum

Reply
 
LinkBack Thread Tools Display Modes
post #11 of 50 (permalink) Old 08-12-2004, 02:25 PM
BenzWorld Member
 
Date registered: Jul 2004
Vehicle: 1989 300E W124
Location: Hampton, NH USA
Posts: 82
Mentioned: 0 Post(s)
Quoted: 0 Post(s)
Send a message via AIM to jmvellis
RE: Which is better gas to fill your car up with--Premium or Super?

plain and simply put...if you run a lower than recommended octane in your car then it will damage the engine. Mercedes-Benz engines have a rather high compression ratio which designates high pressure in the combustion chamber. This means that you must use higher octane fuels (more combustible elements in it that require less oxygen to fire) so that they can fire. Because oxygen is the substance that is actually being burned (after molecularly bonding to the gas particles) it will require oxygen to bond with the particles. The higher the pressure that is in the chamber then the less oxygen that will be allowed into the chamber and the molecules will bond efficiently so that you can recieve the most power from the gas. This is what allows your mercedes to have a high performance engine. This also explains why cars that have lower octane requirements but are run on higher octanes have increases in performance.

Go Sox!!! 2004 World Series Champs!!!
Patriots Superbowl XXXVI, XXXVIII and XXXIX Champions!!! Dynasty!!!
YANKEES SUCK!!! YANKEES SUCK!!! YANKEES SUCK!!!
jmvellis is offline  
Sponsored Links
Advertisement
 
post #12 of 50 (permalink) Old 08-12-2004, 04:26 PM
MTI
BenzWorld Elite
 
MTI's Avatar
 
Date registered: Aug 2002
Vehicle: '85 2.3-16 '99 C280 '11 GLK350
Location: Scottsdale, Arizona, USA
Posts: 4,805
Mentioned: 0 Post(s)
Quoted: 0 Post(s)
RE: Which is better gas to fill your car up with--Premium or Super?

Quote:
jmvellis - 8/12/2004 4:25 PM
This also explains why cars that have lower octane requirements but are run on higher octanes have increases in performance.
If you mean something other than a 1-2 peak horsepower gain, which is felt more psychologically than actually, then I haven't seen any proof for this. All things being equal, running higher octane than your engine needs (with which I aree with you on this) is just a waste.
MTI is offline  
post #13 of 50 (permalink) Old 08-12-2004, 05:24 PM Thread Starter
BenzWorld Member
 
Date registered: Jun 2004
Posts: 87
Mentioned: 0 Post(s)
Quoted: 0 Post(s)
Send a message via AIM to BenzGirl04
(Thread Starter)
RE: Which is better gas to fill your car up with--Premium or Super?

I usually go to Mobile or Getty Station. I dont get about the whole octane thing, could some one explain it to me?! Also, I've always filled my car up with Super, Do you think I should change what Im using for gas? Just Wondering.
BenzGirl04 is offline  
post #14 of 50 (permalink) Old 08-12-2004, 05:40 PM
MTI
BenzWorld Elite
 
MTI's Avatar
 
Date registered: Aug 2002
Vehicle: '85 2.3-16 '99 C280 '11 GLK350
Location: Scottsdale, Arizona, USA
Posts: 4,805
Mentioned: 0 Post(s)
Quoted: 0 Post(s)
RE: Which is better gas to fill your car up with--Premium or Super?

The octane number of a gasoline is a measure of its resistance to premature detonation. Like the other kind of premature . . . premature detonation is not a good thing for your engine. Premature detonation occurs when the octane is too low and during compression of the air/fuel mixture, it combusts before the spark plug ignites and before the piston reaches top dead center. As a result, it pushes down the piston before it has reaches the top of its travel. Much of the gasoline's energy is wasted in trying to move the piston up while the high-pressure gasses are trying to push it down. The extreme temperature and pressure developed can cause broken rings, rod-bearing damage, piston overheating, and erosion of the aluminum. Pistons sometimes end up with holes in their tops from the high temperatures and high pressures. Bad news.

The number on the pump is an average of two other octane numbers. The first is the Research Octane Number (RON) which was the popular standard in the 1960's and derived from less stressful engine testing. Back in the day, those octane numbers ranged from a little over 100 to as high as 104. If an engine is detonating (pinging) at part throttle, it usually needs more RON.

The second octane number is the Motor Octane Number (MON). The MON test is conducted under more severe operating conditions (higher rpm and higher inlet temperature) than the RON test, and as a result, the number is lower. If an engine is detonating at wide-open throttle, a higher MON will usually satisfy it.

The number shown on the service station gas pump is the average of the RON and MON, or AntiKnock Index (AKI). If the sticker shows an AKI of 92, RON is typically between 96 and 97, and MON is typically between 87 and 88. The RON and MON can vary slightly but still must average a minimum of 92 to have a pump posting of 92. Higher octane unleaded fuels will have a greater difference between RON and MON. For instance, 76 Unleaded Racing Gasoline has a RON of 106 to 107 and a MON of 94 to 95, which gives an AKI of 100 to 102.

Higher octane does not necessarily mean more power. If an engine is detonating on 92 octane gasoline, using a higher-octane quality fuel is definitely a plus. If your engine is detonation-free on 92 octane gasoline, the benefit of using a higher octane product is limited, perhaps 1-2 HP due to distillation characteristics.

Aside from premature detonation, some engines may benefit from higher octane gasoline due to high under hood temperatures or in dry climates with low humidity. On a low-humidity, 100-degree day with the air conditioner on, an engine's octane appetite can increase by three to four numbers.

MTI is offline  
post #15 of 50 (permalink) Old 08-12-2004, 09:57 PM
BenzWorld Member
 
Classic_wong118's Avatar
 
Date registered: Dec 2003
Vehicle: 1998 S500
Location: New York
Posts: 73
Mentioned: 0 Post(s)
Quoted: 0 Post(s)
RE: Which is better gas to fill your car up with--Premium or Super?

YES, Super or Premium is octane 93. Regular is Oct.91
Plus is octane 87.
Classic_wong118 is offline  
post #16 of 50 (permalink) Old 08-12-2004, 11:48 PM
BenzWorld Extremist
 
SledDog's Avatar
 
Date registered: Dec 2003
Vehicle: 2004 SLK32 AMG
Location: San Diego, CA
Posts: 807
Mentioned: 0 Post(s)
Quoted: 0 Post(s)
Always use the minimum AKI or octane rating specified

Quote:
Classic_wong118 - 8/12/2004 8:57 PM

YES, Super or Premium is octane 93. Regular is Oct.91
Plus is octane 87.
Available octane ratings are regional. Premium is 91, Plus is 89, and Regular is 97 in CA and a good portion of the west. In some locations Premium is 89 and regular is 85 - I think the Denver area is an example of that, maybe parts of Montana. This is based on what may very well be out dated information that octane requirements decrease at higher altitudes.

MTI supplied some really great information. The one thing everyone forgets is that one gallon of 87 octane gasoline has the same engergy density as one gallon of 91 octane gasoline (or 93 octane). The only real difference is the resistance of the fuel to ignite under pressure all else held equal. As pointed out already, the lower the octane rating (or more correctly the AKI) the lower the pressure the fuel will combust. If the fuel predetinates, bad things happen as previously described. Modern engines can adjust timing to minimize this but it is not a good idea to do this for a prolonged period of time. The one thing I don't remember seeing mentioned is that the fuel may not burn completely and that will leave nasty stuff to build up in the cylinder.

If the energy in the fuel is the same, where does the additional power come from in a higher performance engine? It comes from putting more fuel, along with the right amount of air, into the cylinder. The higher performance engine will have a higer compression ratio in the cylinder. The higer the compression ratio, the more fuel that can be put in the cylinder to be detonated. More pressure in the cylinder means you need a higher AKI so that the spark ignites the fuel and not the pressure. Its the association of the higher AKI fuel and the higher performance engine that seems to cause the misconception that higher octane gives more power.

Current MB engines are designed to use 91. You should use the fuel that is available to you that is at least 91. Going above 91 won't buy you anything. Going below 91 might save you at the pump but you'll lose about the same amount in fuel economy. You'd be better off getting one of those gas cards that gives you 5% and sticking with 91.

MB recommends using gasolines with additives to help maintain the engine. Most of the name brands should be good for that, for example Chevron. There are some other properties of gasoline that can make it worth it to spend a little more especially on really hot days or when your vehicle will be under a heavy load. I still buy my gas at Costco most of the time and at Chevron some of the time.
SledDog is offline  
post #17 of 50 (permalink) Old 08-13-2004, 05:49 AM
BenzWorld Elite
 
lnguyenh's Avatar
 
Date registered: Jan 2004
Vehicle: SL500, CL55, E350, E320
Location: Northern VA, USA
Posts: 3,209
Mentioned: 0 Post(s)
Quoted: 4 Post(s)
RE: Which is better gas to fill your car up with--Premium or Super?

Would "SHELL" be a good gasoline? I have been using Shell (and only) since ... forever. Some told me they are not good but gave no proofs .... Any suggestions? Thanks
lnguyenh is offline  
post #18 of 50 (permalink) Old 08-13-2004, 10:10 AM
Lifetime Premium Member
 
Date registered: Mar 2004
Vehicle: 1997 S600 (sold)
Location: San Diego
Posts: 4,648
Mentioned: 0 Post(s)
Quoted: 9 Post(s)
Lifetime Premium Member
Dude, sounds like an infomercial to sell oxygenated water.

What a crazy set of things to say about combustion in general and in an engine in particular.

The point is fine, though. You need to use higher octane gas for higher compression engines.

Brett
Brett San Diego is offline  
post #19 of 50 (permalink) Old 08-14-2004, 08:38 AM Thread Starter
BenzWorld Member
 
Date registered: Jun 2004
Posts: 87
Mentioned: 0 Post(s)
Quoted: 0 Post(s)
Send a message via AIM to BenzGirl04
(Thread Starter)
RE: Which is better gas to fill your car up with--Premium or Super?

Thanks everyone for the suggestions :)
BenzGirl04 is offline  
post #20 of 50 (permalink) Old 08-14-2004, 10:20 AM
BenzWorld Junior Member
 
Date registered: Aug 2004
Vehicle: 2008 C 300 4Matic 07 SLK 55
Location: DFW Texas
Posts: 13
Mentioned: 0 Post(s)
Quoted: 0 Post(s)
RE: Which is better gas to fill your car up with--Premium or Super?

What has been posted is correct about the use of higher than required octane gasoline--it is a waste! I have a race motor on my motorcycle that makes 700hp and it nothing is gained when I use the 116 fuel over the 94. It all depends what the engine was designed to run on! I am going to put a coupe of gallons of the 116 in the E500 I just bought and see if it helps.

Dave
Boss Hoss 540 is offline  
Sponsored Links
Advertisement
 
Reply

  Mercedes-Benz Forum > General Mercedes-Benz Forums > General Mercedes-Benz

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Mercedes-Benz Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in











  • Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
     
    Thread Tools
    Show Printable Version Show Printable Version
    Email this Page Email this Page
    Display Modes
    Linear Mode Linear Mode



    Posting Rules  
    You may post new threads
    You may post replies
    You may not post attachments
    You may not edit your posts

    BB code is On
    Smilies are On
    [IMG] code is On
    HTML code is Off
    Trackbacks are On
    Pingbacks are On
    Refbacks are On

     

    Title goes here

    close
    video goes here
    description goes here. Read Full Story
    For the best viewing experience please update your browser to Google Chrome