old diesel in fuel tank

Don't think 6 to 8 weeks is excessive but you might want to use a biocide in your tank to stop bacteria/algae etc. [Yes, some bugs can live/grow in diesel - must be tough little b*gg*ers, eh? I believe they live at the water/diesel boundary.]

I've been using Fuel Doctor for a while now (but no commercial relationship). It's an Aust. product and their claims seem reasonable/believable.

I've not done any serious treated Vs untreated tests for smoke, economy, etc. but my sedimenter seems to have a lot less grey sludge in it when I drain it (every 5000 km, at oil change time), since I've been using this stuff.

you're rite that the bug lives at the fuel water interface, best treatment for it is CLADOCIDE or similar. Sorry best treatment is dont get it!! As once it is in there it is hard to get rid of and will cost you lots of filters if you dont strip the fuel system. Keep your tank fuel during the humid time of the year as the more humid air inside the more condensation. Regarding the age of fuel, dont worry about it, diesel doesnt really deteriorate in the short term. Our boats are laid up for 5 months of the year with no probs. More important if you live in a cold climate to be careful carrying over a tankful of summer diesel thru winter.

Don’t be concerned about the age of the Diesel it will last for years, there are emergency generators in city buildings and hospitals that have had the same diesel in them since they were installed ie 10-20 years, the concern is the growth of the "Diesel Fuel Bug", the bug is present in all diesel and will thrive is some places more than others.
The Bug lives on the interface between the water in the bottom of your fuel tank and the Diesel above ie feeding on the diesel and living in the water, so it craps and dies at the bottom of your tank and is then sucked into fuel filters and blocks them, to minimise the growth of the Bug you have to minimise the quantity of water/sediment in the tank. This can be done by draining the sediment from your fuel tank/tanks, not all Diesel tanks have sediment drains on them good 4X4 diesels do ie Toyota’s.
The other thing to do is to keep the tank full, ie up in the neck of the filler when you know you will not be driving the vehicle for weeks, this gives the moisture in the air less contact area with the inside of the tank, the air condenses on the tank inside wall and will eventually make its way to the bottom of the tank and give the bug more room to grow.
I would also suggest that you get the car serviced every 6 months instead of by KM if you are doing less that 10000 a year and if you don’t feel up to draining the sediment have your dealer drain the sediment at the time of service (every six months should be often enough to drain the sediment). And make sure you change the fuel filter at least every year. Filter manufacturers recommend every 6 months for all types of filters but you can get away with 12 months.
I look after a fleet of 60, 4x4 and 70 cranes and small trucks and 60 mining pieces of equipment we burn 100,000 litres a day of diesel and used to have a lot of trouble with the fuel bug so I did some investigation (US army web site) and found out the simplest fix was to minimise the bugs habitat, which is basically draining sediment and condensation out of tanks, up until then we had been buying fuel doctor by the 20ltr container and Wynn’s etc with minimal effect as well as changing fuel filters on a daily basis. Now we don’t change filters outside of service intervals and we don’t use any fuel doctor etc.
Every service sheet instructs to drain sediment from fuel tanks, including storage tanks, problem solved.
Sorry about being bit long winded
Bob

I agree with what the others have said, but will add my 2 bob's worth as well.

As far as I know, it's best to keep your fuel tank as full as practical to assist minimise the chances of bugs forming/taking hold. So I wouldn't be leaving the tank half full/empty for weeks at a time.

I use a Morrisons De-Bug unit to prevent algae etc getting into my filter and beyond. This product was reviewed by Ron Moon in 4X4 Australia Magazine a few years ago. Several months ago Mr Morrison, from Melbourne, was on this forum following my having mentioned his product in another post.

In my particular case, there was insufficient space under the bonnet for me to install the De-Bug unit (it's about the size of a fuel filter and contains powerful magnets). So I mounted mine on the chassis rail of the GU, directly below the driver's footwell. I didn't want to cut into the fuel line to install it, so I simply took the rubber fuel hose off in the engine bay, added a longer replacement piece which goes to the De-Bug unit and then put another hose from the De-Bug unit to the fuel filter. I am satisfied that this unit serves to kill off any algae and other matter that may be in the tank, before it reaches my filter.
On a recent trip to Cape York, my mate in the 3.0L Patrol got fuel at Innaminka at the same time as I did, from the same bowser. Some time later up past Arrabury, his Patrol coughed to a halt......he drained some water from the (genuine Nissan) filter and was able to get the vehicle re-started. My truck has a CAV filter with glass bowl; no sign of any water in my bowl and no problem with engine stopping etc. I know this may have been a complete coincidence.......he may have had water in his tank before this etc.....but to me it's another example that I have spent my money wisely when I bought the De-Bug unit.

I agree totally with the others re time period and the BUG. I also have a CAV filter sustem in my Patrol allowing for any unwanted yuck to be seen in the glass bowl before it blocks up. I also use Proma products which I think are very good. However this does not stop you from getting a bad lot of fuel now & then.
Yeah Nissan does need to put a bung in their tanks.(lowsy Aussie Fuel)

I think you can get something to fix this problem at the chemist. Ask for "geddimeforbyandoffdabike". They may have to make it up specially for you but its worth it.

It works on your central nervous system and reacts with the cheek spreading attributes of a bike seat causing a burning sensation that can only be remedied by sitting on a nice wide and comfortabel 4WD seat and driving somewhere beautiful.

Good luck and let us know how you go. If this spreads too far the NH&MRS may need to be advised.

I hate to say it but the magnetic devices were trialed on fishing boats here in WA and found to be ineffective. As someone previously said, whether it works or not, if it does its job in the fuel lines it is too late. Does it make the dead algae vanish by magic? Where does the sludge go if not into the filter?? Sorry but I am a sceptic too!!

Thanks everyone for your advice.

I'll look into some de-bugging stuff and keep the tank filled up.

R.