I am considering switching to synthetic on two vehicles 1. 2003 Toyota Corrola 20,000 Miles
2. 1998 Nissan Maxima 66,000 Miles
I was told that once you switch to synthetic you cannot go back to dino and that if you switch to synthetic to change the oil after 1000 miles because you are going to clean up the internals in the engine Is this true ????. What would be a good brand to go with ??? I should mention that currently I use nothing but Castrol GTX and change the oil every 1500 to 2000 miles. Yes I know that's overkill but it seem to keep the motor nice and clean. I also add about 4 OZ's of Marvel Mystery Oil when I change it for a little extra detergency. What do you think is it worthwile to switch to synthetic for the purpose of longer engine life or should I keep doing what I am doing ??? Sorry for the long post