Bottled octane boosters can most definitely raise the octane of petrol. To what extent they raise the octane varies from product to product as can be seen in the octane booster shootout. High quality octane boosters can deliver the octane numbers they claim, however there are also a lot of these products on the market which don't deliver anywhere near their claims. A lot of products also advertise their octane gain in points, which are often 0.1RON, so where you think you're getting a 3.0RON increase you're only getting 0.3RON
Whether simply raising the octane of the fuel in your tank is going to give you more power comes down to a lot of variables. To take 2 extremes; if you have an old carburetted 1300cc engine, chances are you will feel little to no difference. However running higher octane fuel in a modern turbo charged car with an adaptive ECU will yield substantial improvements in performance and fuel consumption, especially for cars designed to run on 98+ octane fuel.
This isn't all bad news if you don't have a modern car. Tuning a car on a dyno with higher octane fuel will yield better performance by allowing you to run more aggressive timing and higher boost on turbocharged vehicles.
The most common question about bottled octane boosters is how such a small dose can raise the octane of fuel by such a significant amount. The answer to this lies in the active ingredients. These octane boosters use anti-knock additives which, when added to the fuel, prevent the onset of knock (detonation or pre-ignition). By preventing the knock, the effective octane of the fuel is raised. Although there are many anti-knock additives, we are going to look at the most popular ones.
MMT(Methylcyclopentadienyl manganese tricarbonyl) is used in refineries worldwide to raise the octane of fuel as an alternative to TEL (Tetra-ethyl lead) but is far more environmentally friendly than lead and is not harmful to emission control devices. This is the favoured active compound in most good quality octane boosters.
Ferrocene is an iron compound that is a cheaper alternative to MMT and is also used as an alternative to TEL by fuel refineries, predominantly those in 3rd world countries. Legislation in most 1st world countries (including South Africa) prohibits the use of ferrocene by fuel refineries. This is due to the Iron Oxide which is formed during combustion being highly abrasive resulting in massive increases in engine wear thereby significantly shortening engine life and its propensity for quickly building up on spark plugs causing a short circuit which results in a misfire.
Aromatics such as Toluene, Xylene, Benzine etc. are effective in increasing the octane of fuels, however they have to be used in significant doses to provide a noticeable increase in octane. Dosages of 10% and higher are required and therefore would not be effective in doses of 200ml to 500ml. These chemicals are highly carcinogenic (cancer causing) and are easily absorbed by the skin or breathed in. It is highly advisable to wear a face mask and protective gloves when handling them.
Ethanol is used by some race cars to boost octane. If you wish to use ethanol, there are a few factors you should be aware of.
Ethanol has a different stoichiometric ratio to petrol, which means that the engine will be running leaner. Using anything more than a 10% mix of ethanol (E10) requires that the car be tuned for the fuel. The car will have to be run richer which will also result in higher fuel consumption. Running anything higher than a 50% ethanol dose (E50-E85) will require larger injectors in order to supply the extra fuel required by the engine.
Ethanol absorbs water from the air around it that can cause corrosion and algae in the fuel system. If the car is going to stand for more than a few days, it is advisable to drain the fuel tank.
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