Lifespan of diesel

[MikeT]

Does anyone know what happens to diesel left in the tank for over 9 months?

[myglaren]

Micro biological contamination

Water collecting in the bottom of your fuel tank can be colonised by micro- organisms, these actually live in the water and feed on the Diesel.

If the conditions are right these micro-organisms multiply causing the slimy debris we often see, this will block fuel filters and starve your engine of fuel. This bacteria will, if left, in time corrode the base of your fuel tank.

The best method to deal with this problem is to drain and fully clean the inside of the tank and re fill with clean fuel, the fuel tank should be treated with a biocide at least once a season, your local chandler should be able to help you with this. There are many brands on the market all of whom extort various benefits, and most of whom do the same thing.

An alternative now available is fuel cleaning where a portable fuel filtration system is set up adjacent to your boat which pumps out the fuel from the tank filters and cleans it and returns it into the tank. This service should also be offered in conjunction with a subsequent biocide treatment.

The above is aimed at boat owners but cars will be just the same as condensation can form in any partially filled fuel tank.

I know nothing but imagine that it depends on how full the tank is and how it is vented.

Over time the lighter elements are likely to evaporate and make it less combustible.

Summer diesel may coagulate and go waxy in cold weather.