I had an identical problem about 18 months ago with my ex. The fix was
to introduce 3 teaspoons of Allisons dried active yeast into the oil
storage tank. You can get it from Tesco - it's not organic but seems
to work OK. It's very important how you do this. You mustn't just
chuck it in as it can remain un-dissolved and find its way into your
burner with undesirable results. What you need to do is draw off a
quarter pint of Kerosene from your heating tank and put it in your
airing cupboard for a day or so until it achieves a temperature of 68.8
deg C . Next add 2 teaspoons of sugar to the kerosene and of course
the 3 teaspoons of Allisons dried active yeast. After about 20 minutes
you should have about 1 inch (2.55 cm) of froth on top of the kerosene.
Now is the time. Add the brew to your central heating tank via the
filler cap. You now have to wait for about 2 hours whilst the yeast
converts all the sugar in the tank into alcohol. You should now have a
tank of sugar free kerosene that has the special added advantage as
determined by NASA during deep space probes.