Your oil consumption is not normal. As previously mentioned, have a look at the valve stem seals.
High RPM shouldn't be an issue. At 62 MPH, you engine is turning very close to 2,400 RPM. Do the math if you want. E4OD over drive = 0.721 to 1. 5.13 to 1 rear end gear. 32" diameter tires.
The previous owner of my 95 F53 Bounder used non-synthetic oil for the first 38,000 miles. I switch to synthetic at purchase and now have 125,000 miles on the ol 460. I have used Amsoil, Mobile 1 and now use Syntec from Walmart. They all performed the same. I change oil between 3,000 and 5,000 miles. It's down about a 1/2 a quart at change time.
Synthetic oil does not clean an engine any better than non-synthetic. It has almost the same detergent package. It does not have the waxes that are inherent to non-synthetic oil and flows much better at cold start ups.
Richrd