Marine16 vs Wynns, diesel bug biocide

[cuthound]

16 minutes ago, wakey_wake said:

That is interesting, but with no feasible mechanism for the effect I'm in the "extraordinary claims require extraordinary proof" camp.

 

Car fuel tanks are sealed, presumably with a PRV. You know the hissing noise you get when you open the filler?

I think the aim was to avoid venting the volatile hydrocarbons, for environmental reasons?

It must also reduce the fire risk in a multistorey car park full of petrol cars?

I can't see it does much for diesel but my car seems to have it.

 

One of the devices sold by Marine16 is a desiccant container for the fuel tank. How on earth one is supposed to mount this is anyone's guess, and the eyewatering price for something that looks to be 3D-printed?

 

I would like to replace my 'spider trap' fuel breather with something ducted, through a desiccant trap well above the tank. There are practical issues and presumably also BSS issues. Anyone interested in that?

 

Also the fuel in car and trucks tends to be used up much more quickly than on boats (with the exception of hire and shared ownership boats). Many leisure boats refill once or twice a year or less.

 

Furthermore, these days most cars use plastic for their fuel tanks, so less chance of condensation forming to provide the water/diesel interface that the diesel bug requires to survive.

[Tony Brooks]

1 hour ago, Bee said:

Starting to think that draining the tank over winter might be a better idea than filling it right up

 

That is what the equipment manufacturers told farmers to do with their equipment that only worked on a seasonal basis, when the problems of bug and bio-diesel started to surface.

 

 

[Ex Brummie]

On 16/04/2026 at 17:33, pearley said:

As I have diesel stove I use a fair bit of Marine 16 so buy 1 litre bottles @ £51.95

As a retired service technician for oil appliances, especially vapourising appliances, I would avoid anyadditive like the plague. Any additive reduces the vapourising of fuel, and diesel particularly as a heavier fuel is on the cusp anyway.

I too have an oil stove, and when FAME fuel was introduced, I fell for the additive publicity. The only problem I had was when I added some to the tank. By all accounts it is too easy to overdose which causes extra emulsification and blocked filters. I no longer add anything, and whilst I'm not a heavy user and with only about 2 hours a month of engine running between November and March, I've not had any problem since. I do check the tank for sludge and clear out any I find, which is minimal.

[wakey_wake]

 

10 minutes ago, cuthound said:

Furthermore, these days most cars use plastic for their fuel tanks, so less chance of condensation forming to provide the water/diesel interface that the diesel bug requires to survive.

I don't think the container material is so relevant. Condensation doesn't magically appear on a steel surface just because it's metal, the humidity has to come from somewhere.

 

In the absence of countersunk fuel lids (mine is a proper cap on protruding iron pipe), most of us believe the moisture comes from cycling of humid air through the breather.

 

33 minutes ago, wakey_wake said:

replace my 'spider trap' fuel breather with something ducted, through a desiccant trap

In scribble form, like this

 

Block off the spider sanctuary breather hole and replace it with a longer pipe that dries the incoming air and perhaps has enough volume that the cycled portion never reaches the tank anyway.

 

I can't see a way to avoid drawing fuel into such a breather when the tank is brim-full.

 

Maybe it's simpler and easier to verify BSS to put a desiccant trap around the existing breather? Hmm...

[cuthound]

10 minutes ago, wakey_wake said:

 

I don't think the container material is so relevant. Condensation doesn't magically appear on a steel surface just because it's metal, the humidity has to come from somewhere.

 

The humidity comes from the air in the space between the fuel and the top of the tank. The air gets into the tank through the breather as the fuel level drops.

 

Condensation forms on cold surfaces and as steel is a much better conductor than plastic, will form there first as soon as the temperature drops to or below the dew point.

 

It is astonishing just how much water can collect in an enclosed steel area. Before I learned to leave my bow thruster compartment open (under the cratch cover) over winter. I used to get 5+ litres of water collecting in there over each winter.

 

I pump the bottom of my fuel tank annually and always manage to remove a hundred millilitres or more water from the bottom of the tank.

 

A couple of years ago the mastic seal between the tank filler point and the shell failed and I removed about 20 litres from the bottom of the tank, mainly rainwater that had got through the failed mastic seal.

 

 

[MtB]

1 hour ago, wakey_wake said:

Car fuel tanks are sealed, presumably with a PRV.

 

I'd suggest no they aren't. If they were, when you drive 300 miles in a day and use most of a tank of fuel in five hours, a sealed tank would collapse from the external air pressure on it as the fuel gets drawn out by the fuel pump, but no air can get in to replace it. 

 

I'd say there is always an air vent to admit air when the tank pressure drops, and with the air comes the water vapour which is the source of condensation. 

 

 

[wakey_wake]

4 minutes ago, MtB said:

I'd suggest no they aren't. If they were, when you drive 300 miles in a day and use most of a tank of fuel in five hours, a sealed tank would collapse from the external air pressure on it as the fuel gets drawn out by the fuel pump, but no air can get in to replace it. 

 

I'd say there is always an air vent to admit air when the tank pressure drops, and with the air comes the water vapour which is the source of condensation. 

I believe it would be a bi-directional PRV with a low-ish and possibly asymmetric vent pressures. Yes it needs to admit air to prevent tank collapse, but its purpose is to retain hydrocarbon vapour even on a hot day so I think it will tend towards a positive pressure except when fuel is drawn.

 

(Related but not relevant, this is the purpose of the extra hole in a modern fuel filler. The pump aims to withdraw gas from the tank at the same rate it adds liquid, and the hydrocarbons in that gas are trapped.)

 

I'm not sure of the details but it's something like that.

 

Anyway my bug-relevant point is, how can I retro-fit my boat to prevent humid air entering? Has anyone done it?

[Batavia]

1 minute ago, wakey_wake said:

I believe it would be a bi-directional PRV with a low-ish and possibly asymmetric vent pressures. Yes it needs to admit air to prevent tank collapse, but its purpose is to retain hydrocarbon vapour even on a hot day so I think it will tend towards a positive pressure except when fuel is drawn.

 

Pressure/vacuum vents are fitted to larger gasoline tanks and the opeing pressures are indeed asymmetric - for a smallish tank the pressures might be - 2 mBar for vacuum and + 35 mBar for pressure.  The main aim is to prevent vapours from leaving the tank as the temperature rises - and to prevent the tank from collapsing when the temperature falls.

[Bee]

I used to work for a place that made non genuine fuel tanks for cars. They made a batch without the breather, result was a lot of tanks were returned absolutely flat, the  fuel pump made a pretty good vacuum and then with a big 'boing' the thing collapsed. Bee's tank was in an awful mess a few years ago, it has a bolted plate on it and I extracted everything in it and manually cleaned it, horrible job, since then it has accumulated very, very small amounts of water. Very odd.

I used to work for a place that made non genuine fuel tanks for cars. They made a batch without the breather, result was a lot of tanks were returned absolutely flat, the  fuel pump made a pretty good vacuum and then with a big 'boing' the thing collapsed. Bee's tank was in an awful mess a few years ago, it has a bolted plate on it and I extracted everything in it and manually cleaned it, horrible job, since then it has accumulated very, very small amounts of water. Very odd.

[Alan de Enfield]

9 minutes ago, Bee said:

I used to work for a place that made non genuine fuel tanks for cars. They made a batch without the breather, result was a lot of tanks were returned absolutely flat, the  fuel pump made a pretty good vacuum and then with a big 'boing' the thing collapsed. Bee's tank was in an awful mess a few years ago, it has a bolted plate on it and I extracted everything in it and manually cleaned it, horrible job, since then it has accumulated very, very small amounts of water. Very odd.

I used to work for a place that made non genuine fuel tanks for cars. They made a batch without the breather, result was a lot of tanks were returned absolutely flat, the  fuel pump made a pretty good vacuum and then with a big 'boing' the thing collapsed. Bee's tank was in an awful mess a few years ago, it has a bolted plate on it and I extracted everything in it and manually cleaned it, horrible job, since then it has accumulated very, very small amounts of water. Very odd.

 

 

I suppose it makes sense that if you change companies then you try to find one where you can still use your skills.

As the 'breather problem' happened with both companies do you think that you may have been the common denominator ?

[Tony Brooks]

To the best of my knowledge PRVs are not fitted in car fuel tank breathers, or anywhere else, save the lift pump.

 

Car makers will not fit equipment which is not needed and, as has been said, the high fuel turn over in most vehicles makes bug precautions necessary. There are regulations that limit the amount of hydrocarbons emitted to the atmosphere, but as far as fuel tanks are concerned this is not a problem for diesels, but is for petrol, so nowadays they fit a sophisticated breather system involving charcoal filters and venting to the inlet via a "pulsed" valve operated by the engine ECU. I am rather rusty on this, so things may have moved on.

[wakey_wake]

8 hours ago, Tony Brooks said:

[...] so nowadays they fit a sophisticated breather system involving charcoal filters and venting to the inlet via a "pulsed" valve operated by the engine ECU.

I was guessing, at bi-di PRV. It makes sense that the ECU knows when fuel is being used.

The answer is surely Out There, but for my purposes - I just want to reduce the water going into my tank.

[LadyG]

I was interested in using an injector cleaner, made by same company, any comment about other products?

Edited April 18 by LadyG

[MtB]

3 minutes ago, LadyG said:

I was interested in using an injector cleaner, made by same company, any comment about other products?

 

Wynns have been selling tins of expensive stuff to pour into the various holes in your car for as long as I can remember. 

 

I've never bought any and none of my cars ever seemed to mind.

 

 

[wakey_wake]

1 hour ago, MtB said:

[...]  tins of expensive stuff to pour into the various holes in your car for as long as I can remember. 

I've never bought any and none of my cars ever seemed to mind.

Suppose the big fuel companies realised that diesel bug is a problem, but a bit late. Suppose they now add a biocide when blending fuel.

Marine16 and Wynn's alike would become the new elephant powder... but I'm too scared of being trampled by elephants to not put something in my tank.

 

Maybe I should put samples in jars and see what grows?

 

1 hour ago, wakey_wake said:

I just want to reduce the water going into my tank.

...as much for the rust, as the Bug.