Mobil 1 0w40 FS is BARELY a 40 grade oil, at 12.9 cSt. Even Pennzoil Euro 5w40 is on the thin side, being 12.8 cSt at 100*C. A 30 grade oil is between 9.3 and 12.4 cSt at 100*c.
... Maybe slightly less responsive.
You most likely won't be able to tell the difference between the oils ...
If you really want thicker, step up to a 5w40 diesel oil like Rotella T6 or Mobil 1 Turbo Diesel. These will be in the 14 cSt range.
Not sure you really need that though.