Newbie wants to know...

Howdy , nice forum you guys have here , lots of info available , Congrats on that !! I'm a wrencher , and my daughter just bought herself a 2000 celica GT . It has 166k miles on it and its going through about a quart of oil a week . The other owner runs(still running) Mobil 1 (5w30)synthetic in it . If i where to switch back to dyno oil would it be bothering anything ? Everybody seems so biased on this topic . Most say no , but i believe that the wear on the engine and lesser tension on the rings against the cylinder wall form wear has the rings FLOATING over the slippery synthetic oil thats has coated the cylinder walls ( in my opinion). I guess were going to have to look into another engine in the spring for her .
This brings me to another question.... Does the GTS motor slip into the GT model without too much mods ?? just curious to know As long as were there might as well explore the possibilities ehh ??
Thanks for any input