These deposits on the back of the valve will lower an engine's power and performance.
How Long Will Fuel Live In Your Tank?
The gasoline sold at your local gas station will begin to degrade in a time frame of one to six months after it is blended at the refinery. The factors that help determine how quickly the gasoline degrades are the quality of the gas and the additive package that is blended into the gasoline. The temperature and humidity that the gasoline is exposed to while it is in the gas tank will also cause the gasoline to degrade. As the gasoline begins to degrade, some of the lighter elements that are in the gasoline, such as butane, will evaporate with time, and the fuel will begin to turn into a sticky/gummy/varnish-like substance. Most of the gasoline that you buy at your local gas station contains a component known as olefins, as this gasoline ages or when it is exposed to the heat of an engine compartment it will begin to form sticky gum-like deposits. The deposits left behind as the fuel ages or boils will cause problems with every part of a carbureted or fuel-injected engine's fuel system.
This is a nice illustration of before and after cleaning deposits on fuel injectors, valve
An unleaded race fuel, such as Rockett Brand 100 octane, is designed to have a shelf life of up to two years; part of this longer life is because it contains less than 0.5-percent olefins. Depending on the local and state environmental regulations you have in your part of the country, the gasoline you buy at your corner gas station may have up to 20-percent olefins in it. A gasoline storage stabilizer, such as STA-BIL from Gold Eagle, can also be used to help slow the gasoline's ageing process, but you are ahead of the game if you start with a low-olefin gasoline, such as Rockett Brand 100 unleaded racing fuel.
Adding Performance To Gasoline
There are a lot of additives on the market that claim to add performance to gasoline, but few live up to the claims they advertise. We have recently been working with a new fuel catalyst from Chevron called PurEscape, and it actually did increase the power and drivability in each car we tried it in. The active ingredient in PurEscape is from a family of chemicals known as fatty acid polyols; the exact formula is patented and a trade secret. When the PurEscape is added to the reformulated gasoline of today, both the engine performance and drivability we experienced showed us noticeable improvements. It is normal for a spark-ignited engine to have a certain amount of variance in combustion efficiency from cycle to cycle. The PurEscape improves the gasoline's combustion properties and makes it easier for the spark plug to ignite the fuel in the combustion chamber, and thus allow the combustion process to become more consistent. When the PurEscape is added to the gasoline it will help release the gasoline's energy faster during the combustion process, resulting in higher average cylinder combustion peak pressures.