Fuel that has been sat in the tank. Advice sought.

[Refueler]

Ha ha, thanks. What I was a little worried about was the possible constant condensation building up throughout the colder months because the tank was only half full and where there was plenty of space for moisture to gather. I think that was my thinking really.

Overthinking me ol' fruit !

Scroll on past the scare stories some like to post ...

Throw some enzyme in it and use the fuel.

My 80lt tank - useable vol about 75lt sits every winter with about 20 - 40lt in it .... our weather ranges from +30C in summer to -25C in winter. At start of season - I chuck a bit of enzyme in and go sailing. My breather to tank is an open pipe fitting in cabin side ....

 

[V1701]

The (soltron treated) diesel in mine is approaching 5 years, engine & Mikuni heater running fine...

 

[Minerva]

I'm not convinced about there being an issue around condensation from Air in a diesel tank - the physics does not seem to support this.

Take the Maximum moisture carrying capacity of air - at 0ºC, it's 4.89(10-3 kg/m3) and at 10º it's 9.39(10-3 kg/m3). Source

Now your 90l tank is half full so 45litres of air - If I'm not mistaken this means that at 0º then the maximum moisture in the air is (45/1000)*4.89 = 0.0225g of water and At 10º it's 0.423g of water.

I can't see how half a ml of water could possibly cause an issue.

 

[Refueler]

There is a misconception that its only oil / water interface ... unfortunately many additive web pages dwell on this - maybe because they just stay with what most people believe ?
The reality is MOISTURE and this can be suspended or separate in form of water. It can also be emulsion ... a form of mixed water / fuel that has literally combined.

That condensation in the tank can over time contribute to that 'moisture' ..... but also do not forget 'sweat' ...... ever found a tank with water drops on it ... imagine same inside it.

 

[vyv_cox]

I'm not convinced about there being an issue around condensation from Air in a diesel tank - the physics does not seem to support this.

Take the Maximum moisture carrying capacity of air - at 0ºC, it's 4.89(10-3 kg/m3) and at 10º it's 9.39(10-3 kg/m3). Source

Now your 90l tank is half full so 45litres of air - If I'm not mistaken this means that at 0º then the maximum moisture in the air is (45/1000)*4.89 = 0.0225g of water and At 10º it's 0.423g of water.

I can't see how half a ml of water could possibly cause an issue.

Interesting reading on the subject Does an Empty Marine Fuel Tank Condensate? - Marine How To

I calculated similarly several years ago and decided it was not an issue. I done sure my filler cap is properly sealed and the vent cannot take in water.