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Engine

Fuel heating temperature

How hot to heat a fuel for the injection viscosity your engine maker asks for, from the viscosity on the bunker delivery note.

cSt
°C

Usually 50 °C (bunker delivery note)

cSt

Engine maker: often 10–15 cSt

cSt
°C

Fill in the fields to see the result.

How it works

Viscosity falls steeply with temperature. The standard ASTM D341 (Walther) equation, log log (ν + 0.7) = A − B · log T, is a straight line through any two known points, so the temperature for any target viscosity follows from it.

With only the viscosity at 50 °C (as on the bunker delivery note), the typical slope of residual fuels (B ≈ 3.5) is used; add a second point, such as the viscosity at 100 °C from the analysis, for a better line. Example: 380 cSt at 50 °C reaches 13 cSt at about 135 °C.

Engines usually want 10–15 cSt at the injection pumps (check the maker's figure), and very hot fuel can cause gassing in the system; the viscometer on the fuel module has the last word.

For training and cross-checking. Not a substitute for approved navigation equipment, nautical publications and the ship’s own procedures. Calculations run in your browser and nothing you type is stored; a PDF you download is made on our server and not kept.

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