I use Shell Rotella conventional. I avoid synthetics in my DR for two reasons:
First, there have complaints of notchy shifting with some synthetic oil that were "cured" by switching to dino.
Second, my DR is an '01, and still has the leak prone early base gasket. Mine doesn't leak. Since synthetic oil molecules are smaller, they can weep past gaskets that conventional oil can't. It was a problem on older bikes when synthetics became widely available. Probably irrational of me, but I'd rather not take the chance...
SUZUKI DR650SE INFORMATION INDEX
"...choosing a DR indicates an affinity for peace, harmony and enlightenment. Serenity lies in accepting it as it is, changing what you want, and the wisdom of knowing it ain't orange." -psmcd