Originally Posted by jobrien
But I know that I have heard in the past that if you've run regular oils for most of the time and then you switch to a syn, that you can start burning oil (your car start smoking, etc.)....
This is only true if you go from mineral based, to synthetic, then back to mineral based.
Because everything has swollen up and expanded with the synthetic, putting in a mineral (thinner) oil will be able to seep past seals that the thicker synthetic wouldn't be able to.