Oil gurus: I have a 1998 Chevy Monte Carlo with the 3.1L V6 and a mild case of piston slap. The intake gasket leak has slipped me so far but the car only has 55,000 miles so I will knock on wood. I have been running the Schaeffer's 7000 5w30 in the car for I'd say around 18 months and am well pleased. Could I possibly add a quart or so of the 7000 15w40 to minimize the piston slap or would the thicker oil be a bad thing to do?? I can also go to the 10w30 blend if you guys think it may help. Thanks for any replies.