I have a built 390 FE with the Ford expansion tank and keep it 1/2 full. Never a problem and it stays at that level.
Regarding
synthetic oil...... I use
Amsoil as well as their filters. Swear by it. Our weather here gets pretty cold in the winter and, since I start my car and warm it monthly during the winter, I appreciate the fact that
synthetic gets to the bearings quicker than dino
oil. I'm considering an Accusump device to ease the startup problem (noisy valve train for a few seconds).
My experience with
synthetic oils comes from 16 winters in Anchorage. I never had a V8 bearing failure (several Chevy rod brg failures) once I went with synthetic oils and the engine always started up fine without noise (course we had pre-heaters up there and plugged in all night). I used synthetic lubricants in snow machines, gen sets, cars, motorcycles....everything, and still do. Visit
www.amsoil.com for more info.
Paul