I don't think 'redex' does much - Soltron is the stuff to kill all the bugs and microbes you get inhabiting the interface between fuel and water - yo will always get a certain amount of water in the fuel from condensation etc.
There are of course other additives which to do a similar job - I've added it just for peace of mind, although I've never had any problem with dirty fuel.
<hr width=100% size=1>dickh
I'd rather be sailing... /forums/images/icons/smile.gif
The much-touted additives, such as Redex, are pretty worthless, but give you a glow of satisfaction because you're cherishing your engine.
If you want to add anything to your marine diesel fuel, you'd do yourself and your engine much more good by using one of the bactericide additives available from good chandlers.
I always put in a full dose before leaving the boat for the winter.
If you have a diesel car and it fails its MOT for exhaust emmission the MOT centre or dealer will sell you an additive to clean up the injection system. Car maindealers sell it as well. I have experienced this twice at different places/years and the additive has definately improved performance, fuel economy and emmissions and get through the test. The last brand I used was called "Fortron" and if your engine is very well used and dropping in performance I would have a go with this stuff.
Additives for "billy bug" may be fine but no substitue for frequent use of a proper bottom drain in the fuel tank.
Martin
Biocides are ok but what happens to the dead matter that could block your filters?
Also what happens when your strain of bug develops immunity to your biocide. There is alot more to think about than just killing it as it still poses a problem.