What is Fuel Polishing? Diesel Maintenance
Fuel polishing is the process of filtering and cleaning stored diesel fuel to remove water, microbial contamination, sediment, and degradation byproducts. It extends the usable life of stored fuel and prevents engine damage from contaminated diesel — critical for backup generators and emergency fuel supplies that may sit for months between uses.
How It Relates to Fuel Delivery
Diesel fuel begins degrading within 6-12 months of storage. Water accumulates through condensation, microbes (diesel 'bugs') feed on the hydrocarbons, and oxidation creates sludge and varnish. Left untreated, this contamination clogs filters, fouls injectors, and can cause complete engine failure — often discovered at the worst possible time, like when a backup generator is needed during a power outage.
Fuel polishing systems circulate stored diesel through a series of filters and separators — typically a water separator, a particulate filter (down to 2 microns), and sometimes a UV treatment to kill microbial growth. The process can be done by mobile polishing services or through permanently installed recirculation systems on larger tanks.
For facilities with critical backup generators — hospitals, data centers, water treatment plants, high-rise buildings — fuel polishing is not optional. NFPA 110 (Standard for Emergency and Standby Power Systems) recommends regular fuel testing and maintenance, and many jurisdictions require it.
Why It Matters for BettyJet Customers
If you rely on stored diesel for backup power, fuel polishing prevents the nightmare scenario of contaminated fuel causing generator failure during an emergency. BettyJet can deliver fresh diesel and advise on fuel maintenance schedules for your stored fuel supply.
Frequently Asked Questions
How often should stored diesel be polished?
Industry best practice is to polish stored diesel every 6-12 months, or whenever fuel testing reveals elevated water content, microbial contamination, or particulate levels above acceptable thresholds. Facilities with critical backup generators should test fuel quarterly.
Can I just replace old fuel instead of polishing it?
Yes — for smaller tanks, replacing fuel may be more cost-effective than polishing. BettyJet can deliver fresh diesel and arrange removal of degraded fuel. For larger tanks (5,000+ gallons), polishing is usually more economical than full replacement.
Related Terms
ULSD stands for Ultra-Low Sulfur Diesel — a cleaner-burning diesel fuel containing no more than 15 parts per million (ppm) of sulfur. Since 2006, the EPA has required all on-road diesel sold in the United States to meet the ULSD standard, replacing Low Sulfur Diesel (LSD) which contained up to 500 ppm of sulfur.
Dyed DieselDyed diesel — also called red diesel or off-road diesel — is standard ULSD fuel that has been dyed red to indicate it is exempt from federal and state road taxes. It is chemically identical to on-road diesel but costs significantly less because the tax (typically $0.40-0.60/gallon) is not applied.
Wet HosingWet hosing is the practice of fueling vehicles or equipment directly from a mobile fuel truck rather than from a stationary storage tank. The fuel truck pulls up to each vehicle and fills it on-site — no bulk tank, no pump, no infrastructure required.
Ready to Order Fuel?
Get a competitive quote for diesel, gasoline, jet fuel, DEF, or marine fuel delivered anywhere in Florida.