We have a Vauxhall Zafira 2.0 DTI Life (2004) however recently when I was under the vehicle I noticed a lot of black sludge on the under-engine cover. Upon closer inspection from the engine bay, there is quite a lot of this sludge around the front of the engine (just behind the radiator). I topped the oil up to 4.5 out of 5 on the dipstick, completed a journey of 150 miles and then after leaving the car for 30 minutes decided to check the oil. The oil had gone from 4.5 out of 5 to 2 out of 5 on the reading. Either, this car is losing oil or it's burning it at an alarming rate. What do you think is causing this?