Gashol 95 or 91 Thailand fuel

[spyder8850]

I just returned from Koh Samui and found some interesting and useful facts about Thailand fuel. Hope this helps for those who are going up to Thailand in future. Dug this up from some place...

 

What is gasohol?

 

Gasohol is a motor fuel blend of gasoline and ethanol. Gasohol 95 or 91 is the names of the blends currently available in Thailand, where 95 and 91 are the octane ratings. This fuel is a 90% gasoline, and 10% ethanol, and you might also see this written as E10 which is the European standards for blended fuels (E20 would have 20% ethanol and so on). In some countries like Brazil, Sweden and even in some Midwestern states of US you can buy up to 100% ethanol (mostly E85%) at the stations. This motor fuel can only be used in special designed engines and they use a Flexi Fuel system which detects the blend of the gasohol.

 

Advantages of mixing alcohol with gasoline are that alcohol tends to increase the octane rating and reduce carbon monoxide emissions.

 

Another advantage of the blend is that the ethanols corrosive power helps clean up the petrol system (fuel injection as well as carburetor system).

 

Also the blends ability to absorb water may help to clean up the petrol system.

 

The main problem with the blend is the corrosive power which can cause problems with rubber products. Anyhow the corrosive power is very small and the metal parts are not affected.

 

Theoretically the blend gives a little more power and a little worse mileage. Anyhow the differences are so small that they are difficult to experience.

 

Another problem, maybe not actual for us, is that the blend can split up, especially when contain water, when temperatures change quickly and in very cold climates. This is the reason why gasohol is not recommended for air planes and gasohol can cause some problems in cold climate regions.

 

What is ethanol?

 

Ethanol also called etyl alcohol is the same stuff that make you happy when drinking beer, wine and sprits. It is made from all kind of corps, like corn, grain, sugar, tapioca, palms etc. Actually any bio mass can be turned into ethanol. As a fuel it is very old and already Henry Ford build the Ford T model to run on ethanol.

 

Ethanols chemical formula is CH3CH2(OH) and it is a Hydrocarbon like gasoline. It is soluble in water. Gasoline is not. The water absorbing mechanism is good for your engine if you have problems with water condense in the carburettor. When producing ethanol it is a problem but the ethanol mixed into Gasohol is 99.5% pure. The distribution of Ethanol can cause water absorbing problems but it is not a problem when concentrations are lean like in Gasohol.

 

Ethanol may corrode certain materials. In one way it is good because it can clean up corrosion in the carburettor and fuel systems but on the other hand it may damage old rubber products like o-rings, oil-seals and membranes. Almost all vehicles manufactured during the last 15 years have rubber products that are E10 resistive.

 

What is gasoline?

 

First, gasoline is not a simple chemical compound like water or ethanol. It is a mixture of hundreds of different compounds distilled out from the thousands of compounds that the Crude oil have. Gasoline is recovered when heating up the crude oil from 50C to 200C. There are hundreds of different gasolines that are recovered and by altering the heat interval you get different kinds of gasoline. Common for them all are that they carry 6 to 12 carbon atoms in each molecule. A commonly used average for gasoline is the hydro carbonate Octane (not to be confused with what we mean with octane) which chemical formula is C8H18. The gasolines recovered at the lowest temperature become aviation gasoline, the next group automotive gasoline and then come solvents, jet fuel, kerosene diesel, lubricants, greases, asphalt etc. The gasoline we get is by no way a simple product like etanol. It also consists of much more rubbish than etanol for example sulphur, nitrogen, oxygen and heavy metals. So don�t blame the etanol for logging up the carburator when you fill up your tank.

 

What is octane?

 

We all know that our engines have a compression stroke before it explodes due to the ignite from the sparkplug. During the compression stroke the engine compresses a cylinder-full of air and gas into a much smaller volume before igniting it. The amount of compression is called the compression ratio of the engine and it is the ratio between the compressed volume and the uncompressed volume. Normal ratios for motorbikes is for ex. 1 to 9.

 

The octane rating of the gasoline tells you how much the fuel can be compressed before it explodes by itself causing knocking in the engine. The compression ratio of your engine determines the octane rating of the gas you must use in the engine. One way to increase the power of an engine is to increase its compression ratio. So a "high-performance engine" has a higher compression ratio and requires higher-octane fuel.

The hydro carbonate Octane handles compression very well and has a high compression value. Eighty-seven-octane gasoline is gasoline that contains 87-percent octane and 13-percent of another hydrocarbon heptane with a very poor octane figure. Nowadays the combination of fuels that has the same performance or better of the 87/13 combination of octane/heptane are all compared to the octane of this blend.

 

The race for more performance in the cars started already in the 1920 and all manufacturers tried to invent better gasoline with higher octane so that the engines could handle higher compression rates. So at this time we started to get antiknock additives in the gasoline. They started with Iodine, Aniline but ended up with Tetra Etyl Lead (TEL) which was a very efficient octane booster. The TEL also required a scavenger to remove the lead from the engine resulting in volatile lead halide salts that escape out the exhaust system.

 

The octane booster properties of TEL made it possible for the oil companies to manufacture cheaper (low grade) gasoline and compensate it by ever increasing addings of TEL. In the 1960 some people started to be worried about the lead effects to nature and when the engineers could not find a solution to the problem with lead gasoline and exhaust catalyst the game was over for the lead petrol.

 

The lead gasoline was quickly substituted with unleaded gasoline and high octane gasoline was not available anymore. In the unleaded gasoline TEL was substituted with MTEB. MTBE is the acronym for methyl tertiary butyl ether that is created from methanol (metyl alcohol). MTBE boosts the octane and it is an oxygenate that adds oxygen to the burning process. MTBE also reduces the unburned hydrocarbons and carbon monoxide in the exhaust.

 

MTBE production boomed in the 1990s and as much as 15% of the gasoline could contain MTBE. But then started the problems. MTBE is carcinogenic or cancer causing. For that reason oil companies started to look for substitutes for MTBE and the natural choice was Etanol or pure alcohol.

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SO WHAT HAPPENS WHEN THE GASOHOL GOES INTO THE ENGINE?

 

The answer is quite easy. There is an oxidation process of hydrocarbons fuels that produces energy, water and carbon dioxide. The process is the same is it gasohol or pure gasoline with other additives. The hydrocarbons of the gasoline part of the fuel contains more energy than the hydrocarbons of ethanol. The combustion energy value is about 18.000 (BTU/LBS) for the gasoline and only about 13.000 for the ethanol. This indicates that you loose power when tanking gasohol. On the other hand the Stoichio-metric air-fuel ratio (which means the chemically optimal air/fuel ration) is about 9 for ethanol and 14 for gasoline. This means that that ethanol can accommodate more fuel than gasoline, thus producing more power but worse mileage.

 

Since the 10% blend is very lean it is quite questionable if you can detect the increase in power. Also the ability to take use of the better air/fuel ratio is better on fuel injected vehicles than carburetor models. We are talking about 1-3% increase in power and about the same decrease in mileage.

[scubasimon]

the petrol we have in SG also have additives right? anyone knows what those are? are they similar to ethanol?