The Best Diesel Bug Treatment

By on 1 October 2020 / Leave a comment Updated on: 17th February 2021

Stowing your boat away for the winter, parking the tractor up in the off season or perhaps you just have a diesel car you don’t use often. Leaving diesel in your fuel tank for long periods can really throw up some nasty surprises. As the diesel reacts with the oxygen in the air it will begin to develop sediments, bacteria and even fungi. The nastiest of these bacteria is named “diesel bug” which causes layers of gum and resin to coat the inside of your fuel tank.

As the bug and other sediments found in stored fuel are brought through the fuel system and into the engine it can cause havoc. Filters and narrow pipes can become clogged or damaged, while the engine may struggle to start and run inefficiently once going. What’s more, your engine is likely to lose performance and create copious quantities of black smoke to be emitted from the exhaust.

How Diesel Bug Treatment Will Benefit your Vehicle

Diesel bug treatment (also commonly referred to as biocide or antibacterial diesel additive) is designed to fend off the effects of long-term fuel storage, preventing the deterioration and breakdown of diesel fuel that leads to the growth of the diesel bug. Also treating any other bacteria or sediment likely to form in the tank.

Keeping your fuel in usable condition will mean that when your vehicle returns to use, it will be able to function effectively and reliably. Treating the fuel with a diesel bug additive is also a whole lot easier, faster and cheaper than draining a fuel tank and refilling again when required. Check out the products below for some of the best solutions on the market.

The Best Diesel Bug Treatment on the Market

Hydra FuelPlus Multi-Biocide

hydra diesel bug treatment

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Our first diesel bug treatment additive comes from Hydra, a UK-based manufacturer and supplier of chemical products. You may not see their products on supermarket shelves but they have a good following from specialist industries and chemical experts. Their FuelPlus Biocide product promises to uphold their reputation for class-leading products.

FuelPlus promises to rid all fuels of harmful bugs that grow when fuel is left over long periods, quickly killing unwanted bacteria while also preventing sludge build-up in the fuel tank for over 6 months. This will further help to prevent filters becoming clogged or inefficient combustion occurring as a result of any contaminants reaching the engine.

100ml of product can treat up to 1000L of diesel. Meaning this product will spread easily between a whole fleet of vehicles, farm equipment or any other fuel tanks that will contain stored fuel for long periods.


  • UK-based manufacturer
  • Specialist focus on chemical products
  • Rids fuel of all harmful bugs and bacteria
  • Prevents sludge build up in tank
  • Minimises risk of fuel system damage or blockage
  • Least expensive product listed


  • Lesser known brand in consumer market

Wynn’s Fuel Biocide

wynns diesel fuel biocide

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Next, is a very well-known brand, featured regularly here on Czok, Wynn’s. Their additive lines span everything from octane boosting performance enhancers to oil cleaning additives and everything in between. With many years in the industry, products such as their fuel biocide are sure to be well researched and are a proven hit with customers.

Wynn’s fuel biocide promises not only to protect fuel from the affects of diesel bug but also to cure any existing problems with fuel that has already begun to deteriorate in storage. Application is promised to kill bacteria, algae and fungi, also stopping them from re-occurring. Preventing build-ups in the fuel will help to stop any filter clogging or inefficient running of your engine.

The product should not affect fuel quality meaning optimum performance and no effect on engine reliability. One 250ml bottle can be used on up to 500L of fuel, easily covering small farm fleets, motor boats or diesel cars. The handy dosage device included with the product makes measuring and adding to your fuel tank a doddle.


  • Highly trusted brand
  • Well researched and proven products
  • Can rejuvenate fuel that has already begun to degrade
  • Kills and prevents regrowth of diesel bug
  • Prevents build-ups that will clog fuel filters and pipework
  • Included measuring cup


  • Not a diesel specialist supplier
  • Requires more product per litre then Hydra or NBS additives

NBS Tulen Diesel Bug Treatment

nbs tulen diesel bug treatment

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The last product here comes from NBS, another UK-based specialist chemical manufacturer. NBS focusses a lot of energy on providing products that have minimal impact to the environment, being bio-degradable where possible. They are well trusted by industry experts such as NASA, Rolls Royce and BAE systems. This should give you the confidence that Tulen will stand up well against alternatives with prettier packaging but less impressive performance.

NBS’s diesel bug additive promises to control the effects of bacteria (such as the “bug”) growing within a fuel tank, eliminating existing growths and preventing future bacteria infestation. Preventing the formation of sludge in the fuel tank will help stop any issues with clogging of fuel lines and filters in the system, making for better performance and increased reliability.

As with the Hydra product, 100ml will treat up to 1,000L of fuel, being compatible with diesel, biodiesel and some forms of red diesel also. This product will likely be suitable for use with any diesel storage that may hold fuel for long periods, without effecting quality.


  • UK-based company
  • Manufacturer focussed on emissions and waste reduction
  • Eliminates bacterial growths
  • Prevents blockages in fuel system and filters
  • Suitable for most applications


  • Most expensive product listed
  • Packaging not as attractive as some rivals

In Conclusion

Farm equipment stored over the cold winter, that prized motorboat you love to cruise in the sun with or just a classic diesel vehicle that often resides in the garage. Any diesel-powered motor and fuel tank could benefit from the addition of some diesel bug treatment, keeping your fuel ready for whenever you want to use it.

Don’t let those pesky bacteria ruin your day and cost you big in breakdowns and poor performance. Get on top of any potential issues before they occur and feed your diesel engine the best fuel possible. After all, if you store your equipment correctly, it’ll be ready to rock when you dust off the cobwebs and pull off the covers.

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Jack Gill

Car journalist and fully qualified mechanical engineer, Czok’s newest contributor and long-time automotive writer. Lifetime passion for all things automotive, from new supercars to rusty old hatchbacks. If I’m not behind the wheel, I’m likely under the bonnet or browsing the classifieds. Having spent over 5 years in the automotive industry and under the bonnet of my own car at home, I want to share the knowledge and learning that I have gained, with others without the time to study or the expertise, who just want their car to get them from A to B every day. We aren’t all interested in trawling through endless internet pages and forums. I aim to gather all the information up and roll it into a quick summarised format, to give only the information you really need.

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