I ran QSUD 5w30 in my 2010 F150 (4.6 3v engine). I never had any problems at all, however I noticed after about 50K miles, the dipstick turning like a varnish yellow/brown color. At 105,000 miles I had a lifter fail & had to be replaced. When I removed the valve covers, all the metal components were stained that yellow/brown varnish color which I found to be strange. I convinced my buddy to pull the valve cover of his Honda Civic which he used the 5w20 QSUD & had 140,000 miles on his engine. His was stained the same yellowish brown varnish color. You could scrape half of it off with your fingernail, some wouldn't come off. I haven't used it since. If there was that much discoloration & deposit in the top of the head, I can imagine what the valve & piston deposits looked like.