i have been filiing my car with diesel to the top of the fuel neck........
and have noticed that the fuel cap is getting some brown oxidation on it.
I have noticed this on some gassers that my friends own.

IS this from the diesel fuel or is there water in the fuel as I have been getting my fuel from various stations?
Should I get a new cap or rub this off which is what I have been trying to do?
thanks for reading

Moisture.

H2O and oxygen cause Oxidation - rust.

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You say brown oxidation....is it rust on the steel components of the cap only? if it is then its from H20. If it is a brown slim forming on the plastic components as well then it could be bacteria/fungus. Water vapor is always around and going to corrode some of those naked steel components and even oxidize aluminum no matter what you do. If there is any water vapor in the air inside the tank it can condense on the inside of the cap and cause the rust......Just shake out the cap everytime you fill up. Wipe the corrosion off and then give it a shot of WD-40 once in a while.
If you have bacteria/fungus contamination there are additives you can pick up at any good autoparts store to add to your diesel fuel tank to cure that. Just be prepared to replace your fuel filters after treatment because they will clog from the dead residue left after treatment.
Hope that helps!

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FRED

Daily Driver: 98 E300TD 199K
Hobby Car: 69 Austin Mini
Past Diesels: 84 300SD, 312K
87 300SDL, 251K
94 Chev. K-1500 6.5Ltr.TD, 373K

i was just wondering if i have been getting bad diesel.....as I figured that there was some water in the fuel.
is this common to happen to both the diesels and the gassers.
i have a little on the cap of my gasser w123.

is there anything i should do?

thanks for reading

Brake Fluid and Diesel Fuel attract and absorb water from the Air.

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84 300D, 82 Volvo 244Gl Diesel