Engine restore bottles? haha...you only use that stuff when there isnt a whole lot of life left to the engine...kinda seems like that STOP SMOKE stuff to me....

You should be fine switching to synthetic, trust me, engines appreciate it! It will probably feel like its running a little smoother if you switch to synthetic. Atleast thats what I've noticed in my vehicles...

Mobile 1 10w30 is what I recommend for you(as others did above)