Octel Petroleum Specialties, the UK fuel additive manufacturer, has made a significant breakthrough in the science of predicting the stability of heavy fuel oils. The development could lead to greater efficiency in critical applications such as estimating the oil quality before bunkering and evaluating the benefit of additives for upgrading Bunker “C” fuel oils. Bunker "C" oil is currently produced by blending the oil remaining after the refining process with lighter oil. The main destination for Bunker “C” is ships using diesel engines for propulsion. Traditionally, predicting the stability of Bunker "C" is fraught with difficulty, largely because stability is ill defined and also because previous methods have been somewhat subjective. This, however, is about to change.