[SteveInMD]

Can anyone tell me how fuel stabilizers work?  I always feel like I’m buying “snake oil” when I buy it, but I do anyway in hopes of keeping my equipment operating properly.  Am I wasting my money, or is there science behind these products?  Common sense tells me fuel stabilizer would have to keep the fuel from slowly oxidizing over time, and would have to prevent the more volatile hydrocarbons from evaporating.  Do they do this?s

[Grafter]

Your standard fuel is made of straight and branched, shortish (5-12) hydrocarbons. Long chain hydrocarbons have a high octane rating, and short ones have a low octane rating. Other products, such as cyclic hydrocarbons and benzene may be present, and will have higher octane ratings.

The problem with low octane fuel is that it often spontaneously ignites under pressure at high temperatures (like those in an engine). Now, the engine works by pumping a small amount of fuel into a cylinder, compressing that fuel, then igniting it (with some source of ignition). However, if your fuel is too low quality for the engine you are using, it can spontaneously ignite, which causes two 'firings' of the piston per one injection. This can cause a knocking noise, and is invariably bad for the engine.

Fuel stabiliser is a mixture of the higher octane hydrocarbons, which lower the overall likleyhood of pressure-induced combustion.

By adding fuel stabiliser, you can increase the octane of the fuel you are using, thus reducing the likelyhood of spontaneous (and unrequired) combustion.

Some fuel stabilisers also contain oil to lubricate the parts, if the engine is not sophisticated enough to keep itself oiled (eg your car's engine does this).

So by buying this 'stabiliser' you are increasing the lifetime of your equipment, not the efficiency of your fuel.

[SteveInMD]

Thanks for the reply.  In my case it's diesel fuel I'm curious about which has a centane rating not octane.  So I guess by adding centane I can store my diesel fuel for a long period of time?

[Grafter]

Im pretty sure itll last a similar time whether you add the centane before or after storage. Just make sure you put a cap on it.

[Donaldson Tan]

diesel engine works by compressing diesel at high pressure. diesel undergoes combustion at the act of high pressure. in petrol engines, petrol is mixed with air at high pressure, then an electric spark is used to burn the mixture to drive the engine.

if diesel engines uses a fuel that ignites easily under high pressure, it will inevitably lead to more unwanted 'knocking'. a diesel engine works by self-ignition at high pressure, so it must use centane rating. Centane are less likely to self ignite under high pressure than octane. Diesel engines work under much higher pressure than petrol engine.

[Ski Dude]

I think your question relates more to STORAGE of fuels.  Double bonds in fuels, especially congugated double bonds tend to cause GUM formation and clog fuel injectors, etc.  Some fuel stabilizers tend to prevent the formation of gums by reacting with or "inactivating" the gum-forming precoursers...