ComStar Hum-Out Diesel Fuel Biocide 16 oz
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ComStar Hum-Out Diesel Fuel Biocide — 16 oz
Diesel fuel tanks on boats are a prime environment for microbial growth. Bacteria, algae, and fungi thrive at the water-fuel interface that naturally forms in marine tanks — producing the dark sludge and slime that clogs filters, corrodes tank walls, and causes hard-starting and rough-running engines. Hum-Out kills that microbial contamination at the source.
A single treatment with ComStar Hum-Out eliminates existing microbial colonies and prevents regrowth, keeping your fuel system clean and your engine running reliably. It’s compatible with all diesel engines and fuel system components, and won’t harm injectors, seals, or filters.
Specifications
- Size: 16 oz (473 mL)
- Type: Diesel fuel biocide
- Application: Kills and prevents microbial growth in diesel fuel tanks
- Compatible with: All diesel engines and fuel system materials
- Part Number: CMP-FH0316
Best For
- Diesel-powered boats showing signs of fuel contamination — dark fuel, clogged filters, or rough running
- Preventive treatment at spring commissioning and fall layup
- Tanks that have been sitting with fuel over winter or extended storage
- Any diesel system where water intrusion into the tank is a concern
- Routine annual maintenance on inboard and inboard/outboard diesel engines
How to Use
- Add to the fuel tank before filling — the fuel fill mixes the product throughout the tank
- One 16 oz bottle treats up to 250 gallons of diesel fuel
- For heavy contamination, a double dose may be required for the initial treatment
- Follow all label directions and safety precautions
Parts Desk Insights
Best use case: This is a strong recommendation for any customer with a diesel-powered boat, particularly those who store their vessel over winter with fuel in the tank. Microbial contamination is one of the most common and underdiagnosed causes of diesel engine problems in marine applications — customers often chase injector or filter issues without realizing the root cause is biological. Hum-Out is an easy, affordable fix and a great add-on sale at spring commissioning or when a customer is buying fuel filters. If a customer is already dealing with a contaminated tank, recommend a double-dose initial treatment followed by annual preventive doses going forward.
Shipping information
In-stock and OEM parts: ship same or next business day.
Locally warehoused items: ship within 3–4 business days.
Special-order items: timeline confirmed after order.
Returns & warranty
Returns & Satisfaction Guarantee
We stand firmly behind the quality of every product we sell. Your confidence matters to us — and we back it with a straightforward 30-Day Satisfaction Guarantee.
If you are not fully satisfied, you may request a return within 30 days of delivery. All returns must receive pre-approval prior to being sent back. Unauthorized returns will not be accepted.
To qualify for a return:
Item must be in new, unused condition
Product must be in its original packaging
All parts, components, hardware, manuals, and accessories must be included
Packaging must be undamaged and suitable for resale
Important:
Electronics are strictly inspected. No returns on open-box electronics. Exceptions may apply only with prior written approval. Any electronic unit that has been installed, powered, activated, or altered may not be eligible for return.
We are serious about product integrity — and equally serious about taking care of our customers. If there is ever a product issue, contact us immediately so we can make it right.
For return authorization, please contact our support team before shipping anything back.