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Diesel Fuel Polishing Services

We remove water, sludge, sediment, and microbial contamination from stored diesel using mobile filtration equipment at your site. Fuel stays in the tank. No trucking. No fuel disposal. Serving Fairfield, Vacaville, Napa, and the North Bay.

What is diesel fuel polishing?

Diesel fuel polishing is a multi-stage filtration process that removes physical contamination from stored diesel while the fuel remains in the tank. The fuel is drawn out, passed through filtration stages — coarse pre-filter, water separator, and fine particulate filter — and returned to the tank in a continuous loop until the fuel reaches target clarity and water content levels.

The process addresses contamination that accumulates in any stored diesel tank: water from condensation and humidity, particulates from tank rust and dirt, sludge from fuel degradation, and microbial growth at the water-fuel interface.

Unlike fuel replacement, polishing recovers usable diesel. Unlike in-tank additives alone, filtration physically removes contamination rather than masking it.

Contaminants diesel fuel polishing addresses

Most stored diesel tanks accumulate more than one type of contamination. Effective polishing addresses all of them in a single service visit.

Water

Water enters stored diesel through condensation, faulty caps, and vent contamination. Free water settles to the tank bottom; emulsified water stays suspended. Both accelerate microbial growth and cause injector damage.

Sediment & Particulates

Fine rust, dirt, and tank scale circulate in diesel and collect on filter media. Particulate contamination scores injector tips and wears fuel system components over time.

Sludge

Sludge is a mixture of degraded fuel residue, biological matter, rust, and sediment. It collects on tank bottoms and gets stirred up when the tank is disturbed or fuel is drawn down.

Microbial Growth / Diesel Bug

Bacteria and fungi grow at the water-fuel interface in stored diesel — often called diesel bug or diesel algae. Microbial growth produces acids, sludge, and filter-clogging biomass.

Oxidation Byproducts

Diesel oxidizes over time, especially in partially-filled tanks exposed to air. Oxidation produces gums, varnish, and dark discoloration that reduce fuel quality and injector performance.

Not sure what's in yours?

Start with a fuel sample and inspection. We tell you what we find before recommending any service.

Request Fuel Test

Symptoms of contaminated diesel fuel

Any of these signs in your equipment or stored fuel warrants a fuel inspection.

!Repeated fuel filter plugging or premature filter failure
!Dark, cloudy, or discolored diesel in a sample
!Fuel/water separator filling more frequently than expected
!Hard starting or no-start condition after extended storage
!Engine hesitation, rough running, or power loss under load
!Visible water layer or sludge in a sample drawn from the tank bottom
!Generator that fails load test or does not start on test day

Ask us what we found in your tank before replacing fuel.

A fuel test is the right starting point.

Fuel polishing — questions answered

Fuel polishing circulates stored diesel through a multi-stage filtration system, removing water, particulates, sludge, and microbial contamination. The process is performed on-site — no need to remove or transport fuel.
Duration depends on tank size, fuel volume, and contamination level. A moderately contaminated 500-gallon tank can often be processed in a few hours. We give time estimates after assessing the job.
Polishing removes physical contamination — water, sediment, sludge, and biomass. If fuel has chemically degraded significantly, a lab sample can confirm whether the fuel is recoverable. We advise based on what we find.
Usually not. Fuel polishing is typically performed with the tank isolated from active equipment or during a planned maintenance window. We discuss operational requirements before starting.
Our mobile equipment uses multiple filtration stages including coarse pre-filtration, water separation, and fine particulate filtration. The specific configuration is matched to contamination type and fuel condition.

Clean the fuel before it costs you downtime.

Mobile diesel fuel polishing at your site. Request a quote or call to discuss your tank.