Hi,
I changed the oil on my 4.6, since I only own it for one year it was the first time since it was fresh when I bought the car.
There was 10W40 in the engine before, don´t know which brand. Then I changed it to 10W40 Castrol GTX Ultraclean.
Since then the oil consumption has gone up quite a bit, before I rarely had to top up, now it uses up to 1 litre per 500km if I drive highway speed, normal driving less.
How can that be ? I also observe that the oil is quite black already even though I already "topped up" 5-7 litres in total, so nearly a second oil change by now ;-)
Is it the cleaning properties that make that difference ? Any other ideas ?
I can´t see any obvoius leaks and the engine has run 257,000 km...
Thanky in advance,
Max.

i have noticed that if you change oil brands, motors in general will use oil for one reason or another (usually 1 litre or so) and on the next change stop or reduce the oil loss, strange it is but i dont know why . maybe use an oil additive (lucus oil treatment or similar) and see if that helps , other than that a compression test would be a place to start if you think it's something else

Might be valve seals or rings --- compression test will find issue --- at a wild guess I'd say valve seals /valve guides as they take most heat/wear