My Dad worked as a service manager at a Cadillac dealer. The North star motors were coming out and they took a few new models, and ran them night and day. Using Mobil One Synthetic. After two hundred thousand miles they took them apart and found almost no wear. Mobil synthetic comes in new Corvettes and Cadillacs. Oh, and after ten years my dad remembers replacing six engines. Two were for other reasons. One was for a pin leak from a rear seal. I forgot about the rest. He retired in the nineties. I tend to use Mobil and change my oil twice a year. Usually just before the weather changes.Fresh oil for the cold or the heat.If i put down any amount of miles i change my filter at about five thousand miles. Sometimes i see oil on sale cheap,semi synthetic. and i may change my oil and drive just a bit and then change it again. To flush out gunk.I have most likely made one mistake. I use 10-40 for high mileage motors. I found it lasts longer or seems like it. Thinner oil just seems like water after a little while. I have a Dodge caravan and use a ford pickup filter,it's twice as big. I have read nothing but good things about Motorcraft filters. I think about a bypass filter. I will write about that in another post/section.