This isn't typical but mine has noisier valve train on anything thicker than a 30 weight. It doesn't matter if it's a 5w30 or 10w30, conventional or synthetic (only tried conventional 10w30 recently for about 1000 miles after doing a mmo piston soak over the winter when it was parked). The conventional 10w30 and synthetic 5w30 were both identical in perceived engine quietness. Basically no noise on anything 30 weight. Step up to a 40 or 50 weight and it gets noiser. Not loud, but if you're listening for it you can hear it. I don't feel like mine fuel dilutes bad for a carbureted engine (less than GDI if you can trust a dipstick sniff test) but I won't go much beyond 3k miles or 6-7 months, so 2 oil changes a year. It gets driven almost every day from mid April to mid November depending on when the weather gets better and goes bad in the fall. I figure if using a top grade synthetic twice a year keeps the 43 year old bearings from failing for another 10-20 years then it's worth it. What I'm trying to find out is if synthetic is actually better in that regard. I could run straight 30 grade for half the year if it would be better for wear.