There are several reasons why this happens - most commonly the oil capacity that is quoted is that of a dry fill. The oil change quantity can be quite a bit less especially if the oil is drained and the plug refitted before removing the oil filter.
Other possible reasons are: - The wrong dipstick. A dented oil pan. Considerable sludge buildup inside the engine.
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There are several reasons why this happens - most commonly the oil capacity that is quoted is that of a dry fill. The oil change quantity can be quite a bit less especially if the oil is drained and the plug refitted before removing the oil filter.
Other possible reasons are: -
The wrong dipstick.
A dented oil pan.
Considerable sludge buildup inside the engine.