diesel life and winterizing

[purplehazer]

I bought my boat used about a year ago, and the diesel tank was about 3/4 full. I have no idea how old the fuel is, but I'm guessing a year and a half. When I winterized last winter I put the standard treatment with biocide in it.

Now I'm down to a 1/4 tank and apporaching the winter. For considerations of fuel age, bacteria growth, condensation, etc, should I leave as is (adding treatment) and fill in the spring, fill now (and treat), drain and refill? Or is this even a big deal?

[FrankLanger]

My understanding is that it's best to either fill the tank completely, adding the right amount of biocide, or drain it completely and refill in the spring.
Frank.

[Faster]

The right plan for you might depend on how often you plan to use the boat over the winter season, but definitely keeping the tank full and treated will mimize problems down the road, especially with regard to condensation and moisture accumulation.

[sailingdog]

Leaving the tank partially full will allow condensation to occur. The water/diesel interface is where the algae grows...so it is probably better to drain the tank, or fill it completely, as Frank has suggested, than to leave it at the current level.

Of course, you could leave it at the current level and spend a lot of time cleaning the tank next season, and polishing your fuel.