stored diesel fuel on deck

[bimini blue]

I have a diesel 5 gallon container on the rail , full, from a cruise in June of 2018

is it still good? can I add it to the main tank?

thanks for any advice

[a64pilot]

It’s fine, if and only if it has no “bugs” in it.
Some fuel is sold already treated and a lot isn’t. I treat all my fuel.
I’d at least pour it slowly through a funnel and stop the instant anything odd came through, especially if it looked like phlegm.
Now it’s normal for asphaltanes to precipitate out, they may or will look like black spots in the bottom of the tank if you can look inside of it.
Valvtec fuel is treated, but the chemical used is of a different type than Biobor if and isn’t as effective in my opinion.
A lot or most of fuel and tank issues are biological growth and it’s like seeds, once you get a little in your tank it spreads.