i just swithed to mobil 1 15w-50 oil and noticed that my idle vacuum changed from 15-16 in. Hg to about 14. it has stayed there the last few runs. car idles and runs fine with 67k miles. anyone with similar experience running synthetic?

 

less resistance. i noticed it when i went to synthetic, as well, BUT, i also had a new engine with a SP....

 

My idle came down as well when I switched over, and it became smoother.