drexappeal

Exactly what I was gonna say.

TheBossman

so....BOT from what Ive read its not a good idea to put in octane booster since the car is s/c'ed?...tia

vadim

You sincerely believe that aircraft engines are the same as automotive?

E55AMG99

MORE MISINFORMATION!

DO NOT USE AVGAS in any post 1970 automobile. It contains T.E.L. or more commonly known as LEAD! Also, the vapor pressure of AvGas is different and will lead to cold starting and drivability problems.

Oh, yeah. One more thing. Airports also have 130 octane fuel but the octane rating of Avgas differs from from the stuff you buy for your car. It isn't measured exactly the same way.

E55AMG99

Have you been paying attention? Having a supercharger is not the problem when using additives.

Let me run it down for you.

1. Fuel system, injector cleaners are not necessary since all major brands of gas have some form of detergent already in it.

2. Engine cleaners, carbon deposit removers, combustion and valve deposit removers, etc. are not necessary for mostly the same reason above and the fact that the car is low mileage. New engines run so very cleanly (as close to stoichiometric as possible) that there is very little of the combustion process left behind.

3. Octane boosters come in a variety of flavors but most involve Toluene or some other form of Benzene which have very high 110-120 performance ratings. (Notice I didn't say octane? There is technically no such thing as anything with an octane rating over 100 but that is another lesson.) Both of these are already major components of the gas you buy at the pump. Why? Gasoline, when it is first cracked, consits of about 62% iso-octane (octane)and about 38% heptane. The former has an octane rating of 100 and the latter is zero. Averaged out, you get gasoline with an octane rating of 62. Add in Benzene, Toluene, and a host of other compounds that end in ANE or ENE and you get the crap that comes out of the pump at the gas station. -

Back to the question "What about octane boosters for my S/C motor?" ANSWER- You may or may not need to use them and some may or may not be harmful to your fuel system. How's that for a load of crap? Serioulsy, you need to determine if your driving conditions warrant the need for higher octane. 91 might be sufficient. How to tell? A simple method is to go to Unocal and put in a 50/50 mix of 91 and 100 which makes 95.5 and note your fuel mileage for the whole tank. Also note any other differences but be careful about using your "butt dyno". Most, if not all are notoriously out of calibration. Do the same thing again but use a 75/25 ratio which makes 93.25. If the mileage is the same for both tests, you don't need anything over 93. If both tests are the same as 91, then you don't need any extra octane at all. See how easy that was? While this test is prone to error since the "sample" is so small (you may need to run 2-3 tanks), it will give you an idea of what the optimum octane fuel is for your car, where and the way you drive it.

Now that you have found what octane rating your vehicle likes to drink, you can experiment with octane booster in a can. Look for the types that are safe for catalytic converters (most are) and run some tests similar to above using the recommended ratios on the can. Personally, I've used straight Toluene but I don't recommend it for the novice.

Geez, can we put this issue to bed now before someone else replies with more FUD?

E55AMG99

If anyone is really interested in LEARNING about gasoline, start by reading this.

http://www.faqs.org/faqs/autos/gasoline-faq/part1/

TheBossman

So would you like to be my tutor for my future chem. class next year? haha

Burnt Toast

this thread gave me a nose bleed.

dmatre

Nope. Don't believe they are the same (but similar in principle). Only pointing out that example to demonstrate that 100 Octane does not equal rebuild every 500 miles.

E55AMG99

Only if it involves working with combustible materials!

Trekman

OK I dont care what brand of gas or octane you put in your car! I want to know is it safe to use fuel injector cleaner on A supercharged Benz. and if so what brand?

E55AMG99

If it is safe for a N/A motor, then it is safe for a S/C motor. The bigger question is why do you think you need to?

Moviela

I will accept all of E55AMG99's (nice ride!) technical exposition as correct, but take some exceptions. First I would describe a molecule as a combination of two plus atoms by chemical bonding. While there are certainly more complicated, even more descriptive names for motor fuel, the stuff in its minute form is a molecule. Gasoline is a mix of liquid hydrocarbons -- that is, chemical molecules that contain hydrogen and carbon atoms. The simplest such molecules, methane and ethane, have just one or two carbon atoms respectively, and are gases. The two hydrocarbons of most significance for gasoline are heptane, which has seven carbon atoms, and octane, which has eight. Both are liquids at room temperature. "Straight-run" gasoline -- directly as it comes out of a petroleum distillation plant -- consists of 62-64% octane, and the rest heptane. It's said to have an Octane Rating of 62-64.

Everyone seems to have misunderstood my comment about race car engines being rebuilt often. They are not rebuilt because of the fuel, but because they are worn to the point of not being competitive. They are specially constructed to utilize 100 octane fuel, and need the anti-knock properties of higher octane fuel. Most street cars are not run in competition, and the additional octane would simply be a waste of money. Rebuilding you car that often was ment to be funny!

It was suggested to go to Unocal for 100 octane fuel. That is not possible. Unocal has not operated any gas stations for a number of years. Conoco Phillips refines and markets gasoline at 76 brand stations. As for Unocal itself, for many years they have been living off the '393' patent for reformulated gasoline, and the Supremes (court) have told other oil companies to pay up.
One oil company did not want to play that game, so today Chevron bought Unocal. First no more Texaco, now no more Unocal.

Sorry for any misunderstanding.

E55AMG99

Thanks for the compliment. It is a nice ride.

Back to the topic at hand. The site you (failed to) quote is http://www.avweb.com/news/maint/187232-1.html and it too supports my claim that there is no such thing as a "gasoline molecule". The quote starts with "Gasoline is a *mix*..." as in mixture, not a molecule. Sorry if I seem to be picking nits here. I can't help it.

Now you are making more sense. More octane does not always mean more power. Each car, where and the way it is driven is different and will have different octane requirements. Running more than your car needs is a waste.

Correct. I meant to say 76 - So many of the stations still have the old signs in place and most people still refer to them by their former name. Their website used to show the location of 100 octane fueling stations but alas, some hack has removed the links. They still sell it (so does some Texaco and Phillips) but there isn't an easy way to locate them anymore.

BTW, the buyout of Unocal by Chevron was just approved by the FTC yesterday and as far as the "393" RFG patents, Chevron cannot enforce them in any way under the terms of the buyout. They will become public domain and free for anyone to use unrestricted until they run out. Could this mean lower fuel prices? Hardly!

zedx

I am using (in Australia) Premium Unleaded - Ultra 98 octane fuel in my 91 300E-24 Sportline.
1. Is that TRUE 98 octane?
2. If it is - does my engine (and injectors) really benefit from it, 'cause my pocket certainly dosn't as it costs more than Regular? The Manual states I should use Premium Unleaded but in 1991 there was no 98 octane fuel.

DACHIGGA

Aiight, here's what I have to say. Using a higher octane is not a waste of money.
From a organic chem point of veiw, octane is the most smooth burning of the alkanes in Gasoline. Therefore, the higher the octane the better the combustion. This is because of the physical nature of a molecule of octane. The shape of the molecule and arrangement of carbon atoms causes it to have a very stable structure which allows it to react better with oxygen.

ctC230K

Don't put it in the kompressor, put it in the gas tank.

E55AMG99

You must have been asleep in chemistry class. That is a complete load of I hope your parents didn't pay too much for your education.

E55AMG99

I don't know which of the three common methods of measuring octane rating is in use in Australia. They are Research, Motor and the Average of both or (R+M)/2. The first one is typically higher than the second and hence why we in th USA have decided to use the Average of the two.

Go back to my earlier post about finding the right octane rating for your car. It is a crude trial and error method but it does work fairly well. Using a fuel with an octane rating higher than what is needed will only cause damage to your bank account. On the other hand, using a fuel with too low of a rating can be much more costly.

DACHIGGA

If so, how should it be then? Back youself up.

DACHIGGA

Due to it's stable nature, it can be used for higher compression ratio for engines, I do not know exactly how much octane should be used for whatever compression ratio, but since a high octane gas prevents knocking, it is best to used higher octane.

IT is of coarse best to match the octane with your car as specified.

Tishers

First off let me state my qualifications in this regard;

I worked for Amoco Oil Co for seventeen years. I quit right before it merged with BP (they wanted me to move to Tulsa and I didn't want to). In that time I was an E&I Engineer for pipeline operations, that included the refinery- to -terminal operations. As a common carrier pipeline we moved products for all of the major oil companies. Essentially they leased the pipelines for batching operations to move gasolines and oils through the pipelines to their terminals.

Generally, oil companies do not have dedicated gasoline pipelines from the refinery to terminal. We used the same pipeline to move gasoline as we did to move heating oil, diesel, jet fuel or bunker oil. As you can imagine, to keep Shell's SU2000 or Amoco Ultimate from getting tainted with maritime bunker oil we used some tricks.

What we did was to run a three day oil cycle followed by a four day gasoline cycle in the summer months. In the winter months it was a four day oil cycle followed by a three day gasoline cycle. A the transition between cycles there was always some mixing, this is called "interface". Part oils, usually heating oil, mixed with really cheap, low grade gasolines.

Normally this "interface" was moved back to the refinery for reprocessing but on more than one occasion I left a terminal where a tanker truck had finished hauling away interface, only to see it five miles down the road at a no-name gas station, filling their storage tanks. This is what happens sometimes to uber-cheap regular unleaded.

Now the really important gasolines, like the high grade premiums, basically from all of the major oil companies, are protected in the middle of other batches of gasolines. We had procedures in place that we could NEVER pump a sump tank into a premium batch nor could we mess around with traps, valve line-up's, etc...

The same is true on the oil side, Turbine fuel, or as most people know it, "Jet fuel" is a super clean, low flashpoint diesel fuel. It cannot explode because it has a lower vapor pressure. Turbine fuels were protected in the middle of diesel fuel batches.

Usually these batches were 5000-30,000 barrels (42 gal to an oil barrel) so these are long operations. We would move between 2500-6000 BBL/Hr. Time is money on a pipeline so we had to move quickly but we also had to be perfect in batch seperation. One rotten tank of Turbine fuel and the next thing you know, United Airlines is making you buy back a half a million gallons.

As an E&I Engineer I was responsible for instrumentation and process control. We monitored gasolines with radiation density gauges, Reid vapor pressure monitors, flash point monitors, gravitometers and with random sample pulls that were sent back to the company that owned the batch.

If you really want to look at the quality of the gas you put in your MB then get a glass gravitometer. They are about $50 each, you only need one. What this is going to show you is the API specific gravity or the gasoline batch. Premiums always run about 60-65 API, regulars 54-60 API. Oils are from 54 down to around 30 (thick stuff).

To make premium gasolines the refinery adds more light ends into the product. Gasoline is not a single chemical, it is a mixture of everything in brackets;

hydrogen, methane, butane, pentane, (octane, hexane, heptane....)

The more ligher ends the more volatile the gasoline. It also means that it wants to vaporize quicker and the pressure in your gas tank will increase with higher grade gasolines. It also means that when the injector fires a shot into the combustion chamber there is more atomized..almost..to..vapor that causes a much more effective ignition.

This is not always a good thing... For example, I had a sample batch of Hexane that I left in the tool shed. My husband (now ex) decided that the mower was out of gas and he was to lazy to go to the gas station so he put hexane in the mower. The thing started up and ran like the devil had put a firecracker up it's backside.

He shoulda noticed that the mower never stalled out when he went through the high grass. Nor did it stop when he hit the stop button on the handle. He came inside and said "the mower won't stop". I was thinking of Stephen King in "The Lawnmower Man" (yea, he was that stupid). I went out and watched him try to stop it again.

By now the muffler on the mower was glowing bright red and the fairing above it was melting. The motor no longer needed a spark plug to run. It was pulling in enough fuel (Hexane) through the carb to keep on going. With the rubber boot on the spark plug catching fire he finally put the mower blade down across a 4" x 4" fence post and it killed the motor.

Later that week he took it in to the small engine shop and they dissected the mower. The cylnder head had started to slump and melt. The valves were charred and the rings were fused to the cylnder walls.

The point being, an engine can take so much but once it really starts to operate outside of it's design range then terrible things can and will happen. Minor changes to fuel mixes are fine but be really careful about major changes or in trying to use aviation gasoline in a car. When the catalytic converter gets hot enough it will melt the pallanium matrix inside and block exhaust flow (I have seen the results of that).

from190e_cs

This can void out the warranty

Moviela

Nice Tishers, an articulate accurate post. I am still laughing about the mower!

E55AMG99

I was in the middle of a very lengthy reply when my disk crashed.

Instead, I'll just summarize my post. What you said about Octane (more precisely, iso-Octane) may or may not be true. However, it is irrelevent. You are confusing the compound Octane with the term of the same name for anti-knock capability of fuel. The number you see on the pump is really AKI or Anti Knock Index also known as Octane Rating. To achieve numbers higher than 60-65 (what gas is before further refining and blending) they add other compounds with higher AKI or Octane Ratings, not the compound Octane.

Do you understand now?