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dak dak
Dodge Dakota
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3/19/2004
00:50:45
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 Subject: octane
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Not that i'm complaining but why do they recomend not using gas with an octane rating of more than 87? Just curious
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AmsoilSponsor
DakotaEnthusiast
 
3/19/2004
08:47:27
|  Amsoil Series 2000 Octane Boost - Synthetic Oil
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Most production street vehicles, even high performance ones, are not going to benefit from anything higher than the recommended octane. So it only really becomes an issue if you are unfortunate enough to live in a state that has made unavailable the octane your engine was intended to burn (like California).
Octane rating is a measure of the fuel's resistance to pre-ignition. High-octane is specified by manufacturers when the engine requires it. High compression, high temps, or turbo engines will do better with high octane due to its slower burn rate.
Basically, the numbers you see at the pumps only indicate the anti-knock index of the fuel. It is measured using RON + MON and the divided by 2 (R+M)/2. In short, RON (Research Octane Number) measures the fuel's anti-knock index simulating light load, typical street, normal driving conditions. MON (Motor Octane Number) measures the fuel's anti-knock index simulating high-speed, high load conditions.
They used to post the RON and MON octane numbers in small print on the Sunoco pumps but I haven't noticed this lately.
Run what your owners mauual specifies. Put the high-octane in an engine designed for 87 and you have incomplete combustion ... and a waste of 20 cents per gallon.
__________________________________________________
It’s been my observation that if an engine does not require high-octane fuel, it will run cleaner and better on the fuel it was designed for.
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TOO MUCH OCTANE CAN BE BAD
Right now there is a lot of talk about the highest octane fuel that you can make (or use), especially in the "street racing" fuel business. People relate the highest octane to "my motor is making more power". That is simply not the truth.
One of the downsides to building a fuel with ultra-high octane is that the blend really slows down the flame front in the combustion process. You can get the flame front so slow, that the engine is now running in a "too-rich" condition. This actually takes away horsepower. Bottom Line --- you are slowing down the flame front and getting rid of detonation, at the expense of losing horsepower.
I hear of this all the time from my clients that "street race" --- engines running "heavy" ... and they are trying to tune it to lean it out, when actually the flame front is causing the problem.
__________________________________________________
Steven Roark , Amsoil Dealer , Proud Sponsor of www.DodgeDakotas.com
AMSOIL Synthetic Motor Oils, Lubricants, Filtration, and Truck Care Products
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dak-jak
Dodge Dakota
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3/19/2004
11:35:02
|  RE: octane
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Amsoil " observations " a little off
or misinformed !
Or manufacturer trying to sell more based on
' cheaper ' fuel to be used .
Most of the time you are better off using 89 or
even 91 . Fuel Milage and Performance changes
will verify..
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peter
Dodge Dakota
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3/19/2004
11:45:46
| RE: octane
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I think the Amsoil Guy is correct.
Run what your owners manual specifies.
The compression ratio of your engine determines the octane rating of the gas you must use in the vehicle.
Put the high-octane in an engine designed for 87 Octane and you have incomplete combustion.
The octane rating of gasoline tells you how much the fuel can be compressed before it spontaneously ignites. When gas ignites by compression rather than because of the spark from the spark plug, it causes knocking in the engine. Knocking can damage an engine, so it is not something you want to have happening. Lower-octane gas (like "regular" 87-octane gasoline) can handle the least amount of compression before igniting.
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Sammy
Dodge Dakota
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3/19/2004
12:14:09
| RE: octane
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Are you asking about a high octane gasoline for your truck because you want to improve its performance? If so, you should note, the recommended gasoline for our Dakota (and most cars and trucks) is regular (87) octane. In fact, in most cases, using a higher octane gasoline than your owner’s manual recommends offers absolutely no benefit. It won’t make your truck perform better, go faster, get better mileage or run cleaner.
Your best bet is to listen to your owner’s manual.
The only time you might need to switch to a higher octane level is if your truck engine knocks when you use the recommended fuel. This happens to a small percentage of trucks and cars.
If it was designed for regular gas, but knocks, often that means you need a tune up.
Unless your engine is knocking, buying higher octane gasoline is a waste of money.
However, some vehicles with high compression engines, like sports cars, old cars and certain luxury cars, need mid-grade or premium gasoline to prevent knock.
How can you tell if you’re using the right octane level? Listen to your truck’s engine. If it doesn’t knock when you use the recommended (87) octane, you’re using the right grade of gasoline.
If your engine runs well and does not knock or ping on low octane gasoline, there is no advantage in switching to higher octane gasoline.
If your engine knocks or pings, it does not necessarily mean something is wrong with the gasoline. It could be a problem with the truck's ignition timing or exhaust gas recirculation. On high mileage engines, a carbon build-up in the cylinders can increase cylinder pressures and cause knock.
A few engines may knock or ping - even if you use the recommended octane. If this happens, try switching to the next higher octane grade. In many cases, switching to the mid-grade or premium-grade gasoline will eliminate the knock. If the knocking or pinging continues after one or two fill-ups, you may need a tune-up or some other repair. After that work is done, go back to the lowest octane grade at which your engine runs without knocking.
Our trucks are designed to run on 87 octane gasoline, and a high octane gasoline will not improve mileage. If switching to high octane gasoline does improve mileage, you might find that a tune-up will give you the same improvement on 87 octane gasoline.
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dak-jak
Dodge Dakota
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3/19/2004
13:08:11
| RE: octane
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Are you all fools? Did you not read what I posted? Obviously I am right so please stop with your long winded responses and just take my post for the fact that it is.
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Timberwolf
GenIII
3/19/2004
14:01:20
| RE: octane
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Dak-jak, actually they are absolutely correct. Running a higher than required octane will decrease horsepower, fuel mileage, and eventually ruin your catatlytic converter and oxygen sensors because of all the unburned fuel going out the exhaust. Two variables are important here, compression ratio and temperature. Increase either of these and you will need higher octane. If you have done no performance mods and you are getting knock, Dodge offers a PCM flash that will take care of it. If you have significant mods, you may have to run higher octane. Bottom line is that I am not paying for your fuel or maintenance costs, so do whatever you want. Just don't tell others to do it or you will cost them money too.
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uh...wolf
Dodge Dakota
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3/19/2004
16:42:47
| RE: octane
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not quite right dude. there is NO unburned fuel going out the engine when octain is higher then required no does it harm in anyway to the cat either BECAUSE NO UNBURNED FUEL GOES OUT THE ENGINE.
However one thing you say is absolutely right , ther WILL be a performance decrease as higher octain fuel has a SLOWER BURN RATE, and not for any other reason, The fuel burns slower so a lower or standard performance engine will tend to, at high speeds, open the exhaust valve before all the fuel is burned, BUT the burning of the fuel continues after the valve is open, thus wasting any unburned but still burning fuel as excess energy escaping out the exhaust system and not pushing the piston. By the time the flame from the fuel reaches the cat it is already burned, but because part of the flame happened in the exhaust manifold instead of the engine, the exhaust gas temp is a bit higher and THAT is what causes the cat to burn out early. So in a round about way you are right, but not in the specific details.
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no
Dodge Dakota
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3/19/2004
18:28:57
| RE: octane
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If you think that a richer mixture, caused by higher than required octane and thus a slower burning fuel/air mix, will produce a higher exhaust temp you could not be more wrong.
Higher than req. octane will not, can not increase the exh. temp, it will DECREASE it in a similar way to enrichening the mix with more fuel will.
Your statement about how the fuel is 'burnt' before reaching the cat is flawed as well. Incomplete combustion caused by too high of an octane fuel will cause incomplete combustion in the cylinder allowing partly burnt gasses to enter the cat where the operating temp of the internal materials far excede that of the relativly cool manifold. The whole idea of a cataylitic convertor is that it combusts the gasses in the exhaust, reducing emmisions, if the exhaust contains more hydrocarbons than the design allows the temp increases beyond the tollerance of the cataylist material.
Sorry for long post, but...
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uh ..no
Dodge Dakota
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3/20/2004
11:09:32
| RE: octane
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sorry to inform you guy but I work as a chemist for SUN OIL COMPANY better known in retailing as SUNOCO and I dammmed well know what I am talking about and YOU not I got it very wrong.
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no
Dodge Dakota
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3/20/2004
11:15:59
| RE: octane
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huh? can anyone make sense of that?
"and YOU not I got it very wrong."
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lmao
Dodge Dakota
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3/20/2004
11:17:37
| RE: octane
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LOL! The only Sunoco you work for is the one that's open 24 hours at 5th and main!
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