If you open the engine bonnet when the engine has overheated or during a fire in the engine compartment, you could come into contact with hot gases or other escaping operating fluids.
Components in the engine compartment may continue running or start up suddenly, even if the ignition is switched off.
Make sure of the following before performing tasks in the engine compartment:
Certain component parts in the engine compartment can be very hot, e.g. the engine, the cooler and parts of the exhaust system.
bonnet
oil dipstick
engine oil filler opening cap
washer fluid reservoir cap
coolant expansion reservoir cap
The engine oil becomes dirty during operation and loses quality and also gradually loses volume. Check the oil level regularly and top up the oil or have it changed if necessary.
Regularly check the fluid level and the major assemblies for leaks. If you detect fluid loss, e.g. oil flecks on the vehicle parking space, consult a qualified specialist workshop as quickly as possible.
out of the dipstick tube. using a lint-free cloth. back into the guide tube as far as it will go and pull it out again. If the level is between MIN mark 
and MAX mark 
, the oil level is adequate.
and top up the engine oil and depends on the engine: Diesel engines with front wheel drive approx. 2.5 l
Diesel engines with rear wheel drive approx. 2 l
Petrol engines approx. 1.5 l