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What this video covers

Nigel Calder explains why the decades-old advice to fill a diesel tank before winter layup no longer holds for modern biodiesel blends.0:56 FAME-based biodiesel, now standard across Europe and common in the U.S. at blends as low as 5% that pumps are not required to label, absorbs moisture, degrades quickly, and has a storage life under one year.1:29 For a sailboat with a 300-liter tank whose owner burns far less than that annually — the specific scenario posed — Calder recommends filling only what you expect to burn that season and running the tank as low as practical before layup.2:00 The old full-tank logic aimed to prevent moist marine air from condensing water inside an empty tank through the vent; Calder acknowledges that risk but says biodiesel degradation now outweighs it.1:07 He also recommends installing a fuel sampling point that reaches within an eighth of an inch of the tank bottom, so that at the start of each season any condensed water or sediment can be drawn off before the engine runs.2:23 The Yanmar 4JH2 owner's manual recommendation to fill for storage is cited as the conflicting guidance the questioner was navigating.0:16

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