What is the mixing ratio considered as 'light'?

A mixing ratio considered as 'light' refers to the proportion of fuel to oil in a mixture. In aviation and especially within the context of plane captain responsibilities, this term is significant because it affects the performance and maintenance of aircraft engines.

When we refer to a mixing ratio like 1-9, it means that for every part of oil, there are nine parts of fuel. This ratio is classified as 'light' because the amount of oil is significantly lower compared to the amount of fuel. A lighter mix tends to reduce smoke emissions, lower the likelihood of fouling the engine with excess oil, and generally enhances engine performance by ensuring that fuel combustion is more efficient.

In contrast, other mixing ratios, like 1-1, 1-3, and 1-4, involve a higher proportion of oil in relation to fuel. These ratios can lead to a richer mixture, which may result in increased engine deposits, higher emissions, and could affect the overall performance negatively. Therefore, the 1-9 ratio stands out as the optimal choice for a 'light' mixture, which is essential for peak operational efficiency and long-term maintenance of engine health.