Dont ever use any oil stop leak in an engine. Its not meant to be in there.
Synthetics will amplify any leaks 10 fold. With dino oil, the molecules are all different sizes and with synthetics, the molecules are still oil molecules, but smaller and all the same size. They creep through every seam if the seal isnt perfect. I dont like running pure dino oil, but pure synthetic causes major leaks everywhere on my engine, so I run Q high rpm sythetic blend, and so far, so good. A thicker oil wont leak out of the seams as easily, but will raise the oil pressure. My next change, Im thinking of going with my own blend. 2.5 quarts of 20w-50 and 2.5 quarts of 5w20. If they mix (dont know if they will mix properly), Ill end up with 12.5W-35. Thicker oil quiets my engine down alot and reduces oil consumption alot, but I think the 20W-50 Im running is too thick, and the 10W-30 makes my engine noisy and it starts burning oil...like 1 quart every 1500 miles, so I want to try something in-between. We'll see how it turns out.
