depends sa running hours mo... for long distance travel... cool down ka muna before swithcing off... pero kung sa pangmalapitan lang... off mo na...
By the way,, FYI lang... Diesel engine is not for long idling.... basta nasa Normal operating temperature na sya.. if possible iload nyo na kaagad... long idling will cause unburned diesel to mix with your oil... parang dillution na rin yun ng engine oil and diesel.....
although oil din ang diesel, pero yung viscosity nya ay di gaya ng engine oil... it will affect your car's internal parts...