Ignoring the recommended interval is extremely risky. Cam belt failure on an interference engine (like many diesels) can cause catastrophic and expensive engine damage. It's far better to replace the belt *before* it breaks than to risk a major engine rebuild.
If you don't have the owner's manual, try searching online for the specific engine code (found on an engine plate usually near the engine or in the service book) and "cambelt replacement interval". This might give you a more precise answer, but remember to treat any information found online as guidance, not a definitive replacement schedule. The owner's manual takes precedence.
