Government mandates for renewable diesel-specifically Hydrotreated Vegetable Oil (HVO)-are being fast-tracked for heavy equipment on public works projects. HVO is chemically identical to traditional petrodiesel at the molecular level, burns significantly cleaner, and can be run in a standard diesel engine without any modifications to the fuel system. At least, that is what the fuel distributors and OEM marketing departments claim. The reality on the shop floor is far more destructive.
While HVO is a fantastic fuel for combustion, it has a drastically different solvent property than the sulfur-heavy diesel these machines burned a decade ago. HVO acts as a powerful detergent. When a contractor pours HVO into an older machine that has run standard diesel for 10,000 hours, the fuel immediately begins dissolving the layers of varnish, sludge, and lacquer that have peacefully coated the inside of the fuel tanks and lines for years.
This chemical scrub releases a blizzard of dissolved sludge straight into the fuel filters, plugging them within hours. Worse, HVO has a severe shrinking effect on traditional NBR (nitrile) rubber. The O-rings in the fuel filter housings, the lift pump seals, and the injector return lines-all designed for the swelling properties of old diesel-dry out, shrink, and crack. Contractors are switching to HVO and suddenly finding their shop floors swimming in fuel leaks from every fitting on the machine. To safely run HVO in an older fleet, mechanics must preemptively replace every single fuel system seal with FKM (Viton) or EPDM equivalents, and change the filters three times in the first month to catch the liberated sludge. The fuel may be "drop-in," but the maintenance bill certainly isn't.
