Before we can start to look for the reasons behind the loss of oil, it is first necessary to define various terms in more detail. Normally, the term "oil consumption" is always used in a very general sense. However, in the workshop it is necessary to make a distinction between the loss of oil and the actual oil consumption.
A specialist only uses the term "oil consumption" to describe the quantity of oil which enters into the combustion chamber where it is then burned or coked. The term "oil loss" is used to cover all of the oil lost through leakage throughout the entire engine.
Bigger oil leaks are always visible when looking at the engine from below. Engine components will be covered in oil and dirt. Oil leaks always go downwards and backwards, so tracing of the oil leak is done by going upward and forward until engine components are found clean and dry.
Oil consumption can be identified by looking at the spark. A good spark combined with a good combustion will result in a light brown or a greyish/white tip. A black & ashy or a wet with oil spark plug tip (and the last few spark plug threads) is proof of oil entering the combustion chamber and burning.
Primary reasons for oil loss:
Leaking oil radial seals (on a rotating shaft)
Primary reasons for oil consumption: