What gas do you use?
 

I have recently bought a 92' 300E with 183K miles. The owners manual says to use nothing less then 91. I know one mercedes dealership told a friend of mine who bought a 96' that if he didn't want to put a new engine in it he definately should run premium in it. I wanted to get the forums opinion.

Fiz123
92' 300E

Shell V-Power.

Nothing destroys an engine more thoroghly than cheap gas!

I have used nothing but regular unleaded in my 1986 560 SEL since it was new. Engine runs fine at 148K miles. That being said, if you plan on doing lots of hard acceleration, trailer pulling, or high speed driving then you should be using premium.

I agree with using Shell V-Power and short of the availability of that, I go to Mobil, Sunoco, Marathon, but always 93 Octane.

Owners manual for the 5.6 litre demands premium fuel
 

For the past ten years, ONLY Chevron Supreme Unleaded, never a drop of anything else, never! No exceptions there- the car lives a HELL of a lot better than I do :) :confused:

It costs more, but the result is that at 117,000 miles the injectors are just fine and the car has always run beautifully, never a problem, under any condition.

I have heard that Chevron Supreme with "techron" additive supposedly cleans the injectors as you drive, and that gas has worked well for me, and I guess I will still keep with it, it's easy available anyplace in California, though its not cheap..

Jim

The station on the corner used to be Citgo, changed to Mobil a few weeks ago, but I buy their 93 octane and have never had an issue...keep in mind, in the midwest we have had 10% ethanol in our fuel for years and I wonder what that's doing to my cars?!

I always run Premium from either 76, Chevron, or Shell. I sometimes use a place called Valero, but that is if my fuel light is on.


Oh, and I do splurge for 105 octane. I run a few gallons a month just to make sure she is in great running order.

105 octane? That's a no-no around here. The place on the corner sells 100 octane "racing fuel" but you can only put it in a car that's on a trailer, it can't be on the ground. I've seen people pull a trailer up to the pump, and roll multiple cars onto the trailer to fill them up, so I guess the station is within the letter of the law.

You are just allowed to pull up and fill up. The reason why I only run a few gallons is that it is almost $6.00 a gallon. I ususally run it once a month, or twice if I am going to take her to the race track. She runs sooooo perfect on that gas. The slight miss at idle is gone, and it is just soooo silky smooth. Its a totally different car when you put that gas in.

We filled up the 600 with a tank of 105. The engine was running soooo smooth, and felt super powerful. It was truely a fire breathing beast!

depending on the compression ratio of your engine if you run gas with higer octane than required you are just wasting your money. so when the number goes up so does the fuels ability to be compressed before it spontaneously ignites. so technically 105 octane will burn slower than say 87 octane or 105 is less volitile than 87.

http://auto.howstuffworks.com/question90.htm


If you've read How Car Engines Work, you know that almost all cars use four-stroke gasoline engines. One of the strokes is the compression stroke, where the engine compresses a cylinder-full of air and gas into a much smaller volume before igniting it with a spark plug. The amount of compression is called the compression ratio of the engine. A typical engine might have a compression ratio of 8-to-1. (See How Car Engines Work for details.)

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.

The compression ratio of your engine determines the octane rating of the gas you must use in the car. One way to increase the horsepower of an engine of a given displacement is to increase its compression ratio. So a "high-performance engine" has a higher compression ratio and requires higher-octane fuel. The advantage of a high compression ratio is that it gives your engine a higher horsepower rating for a given engine weight -- that is what makes the engine "high performance." The disadvantage is that the gasoline for your engine costs more.

The name "octane" comes from the following fact: When you take crude oil and "crack" it in a refinery, you end up getting hydrocarbon chains of different lengths. These different chain lengths can then be separated from each other and blended to form different fuels. For example, you may have heard of methane, propane and butane. All three of them are hydrocarbons. Methane has just a single carbon atom. Propane has three carbon atoms chained together. Butane has four carbon atoms chained together. Pentane has five, hexane has six, heptane has seven and octane has eight carbons chained together.

It turns out that heptane handles compression very poorly. Compress it just a little and it ignites spontaneously. Octane handles compression very well -- you can compress it a lot and nothing happens. Eighty-seven-octane gasoline is gasoline that contains 87-percent octane and 13-percent heptane (or some other combination of fuels that has the same performance of the 87/13 combination of octane/heptane). It spontaneously ignites at a given compression level, and can only be used in engines that do not exceed that compression ratio.

During WWI, it was discovered that you can add a chemical called tetraethyl lead (TEL) to gasoline and significantly improve its octane rating above the octane/heptane combination. Cheaper grades of gasoline could be made usable by adding TEL. This led to the widespread use of "ethyl" or "leaded" gasoline. Unfortunately, the side effects of adding lead to gasoline are:

Lead clogs a catalytic converter and renders it inoperable within minutes.
The Earth became covered in a thin layer of lead, and lead is toxic to many living things (including humans).
When lead was banned, gasoline got more expensive because refineries could not boost the octane ratings of cheaper grades any more. Airplanes are still allowed to use leaded gasoline (known as AvGas), and octane ratings of 100 or more are commonly used in super-high-performance piston airplane engines. In the case of AvGas, 100 is the gasoline's performance rating, not the percentage of actual octane in the gas. The addition of TEL boosts the compression level of the gasoline -- it doesn't add more octane.
Currently engineers are trying to develop airplane engines that can use unleaded gasoline. Jet engines burn kerosene, by the way.

105 ???
 

jeeze only stuff we ever gotten in norway was 98
Now we can choose
98 leaded, 97 unleded, 95 unleaded and 92 unleaded

but thats it...

Sunoco stations used to have pumps that dispensed all sorts of octane ratings, 6 or 7 as I recall. We don't have Sunoco around here anymore so I don't know if they still do that. I always wondered how they did that...did they have additives that were added at pump-level to the fuel in the underground tanks?

Racing fuel is great marketing placebo for the alter-ego hotrodder who believes his car runs "better" or "has more power" when running it. If your car's not pinging with 98, going to 105 is just throwing your money away. But hey, if it makes YOU feel better...

No, its because it just idles that much smoother when I put it in there, and run a bit through. I always use good quality gas, and never get pinging.

However, I run a few gallons to burn off excess carbons, and to clean the motors internals.

the octane really does nothing for deposits or carbon buildup it isn't a cleaner.
it is possible that the high octane gas you use has more cleaners and other detergents that clean up the system, adding techron to the tank periodically or using a gas like chevron which contains techron might be more cost effective and produce better results.