According to my clymer's manual, it says to use SAE 30 oil. I got some from wal-mart. The oil filter I got from Advance Auto, who also could get plugs, wires, and light bulbs for the bike. The oil filter was 4$.
In Australia we use 20W50 due to the very harsh climatic conditions here. I have used Mobil 20W50 since new and the oil filter I still get from my local Honda dealer. Most bikes in Australia use standard oils , but the latest are leaning towards these new Synthetic Oils. Over priced at $60 for 5 litres which is what my 750 holds, but only pay $25 for Mobil 20W50.
I work at autozone and someone lied to you man, if you give them the part number they can cross reference it. i get my 81 cb750k filter from work for about $4.50 before my discount. the only thing is that they have to special order it but it comes in in about 2 or 3 days, but if you come in a couple of days before your lookin to change your oil you'll have no problems