Water in Gas-Self Sealing Caps

[DANNOV]

I have a 1985 911 (my car) and a 1995 Corvette (my wife's car). Both cars have aftermarket self sealing gas caps, i.e. the kind where the gas filler nozzle is inserted through a spring load flap. I put these caps on my cars so that my wife could fuel up with a minimum of inconvenience (to keep her hands clean). This was a big mistake. Last week the Corvette had a serious problem with water in its fuel tank. A $700 repair!
After this big repair I tested the cap by putting it on a sheet of absorbant paper and slowly pouring a small amount of water onto the spring loaded flap. The water went through immediately! It was far from water tight. The Corvette is especially vulnerable because the gas filer is on the rear deck in a recessed area that easily fills with water. But, when washing my 911 I have noticed that the area under the gas filler door gets wet, this concerned me but I never thought that water could get into the tank. I understand that getting water into your gas on a Porsche can cause big and expensive problems...Bruce Anderson has discussed this problem several times. Also, we have ethanol here in the midwest and that compounds the problem because it is a magnet for moisture. My 911 is still running OK but the aftermarket gas cap is gone, it is not worth the risk! I would suggest that anyone using these caps be very careful.

[Zendalar]

In Finland we have to use the fuel additives to keep out the water from our tanks, and stop the water from freezing. Temperature differences at fall/spring can be 30 degrees celsius when comparing night/day.

These additives cost about 2$ per litre and you just add half litre to full tank and the water is being mixed with the additive and gasoline. This same thing prevents the carburetors freezing near/below zero celsius. These also remove some residues from the valves and keep the "places" clean.

Very advisable additive to use.