OK I use Castrol oil can I change it to the Mobil 1 or would this damage my car because of the transition

 

Your engine won't know the difference in oil brand. Analogous to filling up with Shell, Chevron, etc...

 

I've actually blended different oils to get better additive packages, I don't recommend it but you can mix oils without issue.

 

Here is the issue I have, metal will absorb some oil, it changes the metallurgy of said metal. It's the reason you can't weld a baffle on a used oil pan. When you change oils, the oil that has saturated into the metal can be wiped away by conflicting additive packages. Which is why amsoil says that when switching to amsoil from another brand, that you treat that 1st oil change as severe service.

My car (2002 Ap1) has used castrol edge for most of its life and it burns about a quart every 2300 miles, every time I try a new oil brand consumption goes up to 1qt/1000mi I've tried Mobil1 Pennzoil Amsoil, even different weights, 10w-30 castrol edge burns the least of all.

 

If it bothers you, just make sure it is warmed up before the change and let it drain thoroughly. (Go away and have some beers) Easy to do if you are at home.