Back to Regular Oil - Bad for Engine?

[bertypower_imp]

Alright... I was talking to the parts guy at my local Honda dealership. I said that I wanted to go back to regular oil in my CB1100. Previous owner used synthetic. He said that I could ruin the engine if I did so. I’ve seen posts on here about people going back and fourth. Can you guys who have done so clarify this? Thanks!

I plan on changing the oil about every 3-4000 miles.

Thanks!