What mixing ratio would be considered 'heavy'?

'Heavy' mixing ratios typically refer to a higher concentration of oil to fuel in aviation contexts. A 1-1 mixing ratio indicates equal parts of oil and fuel, which results in a denser mixture that can be considered 'heavy.' This type of mixture is often used for specific applications where lubrication or protection is required, such as in some two-stroke engines, to ensure that the engine runs smoothly and to prevent wear.

On the other hand, the other ratios—1-4, 1-9, and 1-10—indicate a greater proportion of fuel compared to oil. These ratios would be classified as 'light' or 'normal' mixing ratios, suitable for different operational needs. In summary, a 1-1 mixing ratio is recognized as 'heavy' due to the balanced quantity of oil present in relation to fuel, which plays a critical role in engine performance and longevity.