1978 engines were set up to run on unleaded fuel. You can run unleaded,,and I would recommend running the mid-grade to help prevent pre ingnition as motorhome engines work very hard and are running at high tempratures most of the time.
Regular unleaded should be fine, but if your engine knocks, deisels, or pings, try using premium or add an octane booster. The Windsor is a good, solid engine that can take a lot of abuse. The type of gas you use will not damage it in any way. The level of octane will only affect the performance slightly.
" regular " unleaded ( 87 octane )
It depends on if you like Windsor or not.
93 octane
Each car should have a recommended fuel octane in the owners manual.
" regular " unleaded , 87 octane
87 octane should do fine. If you find it knocks a little then go to 89 octane. You can always use 91 octane, won't hurt, just in the pocket book.
regular unleaded 87 octane
" regular " unleaded , 87 octane
Premium unleaded 98 Octane
" regular " unleaded , 87 octane
" regular " unleaded - 87 octane