Is there any way to determine if a synthetic oil or conventional mc oil has been run in a bike you purchase used from a dealer?

 

short answer is no

unless you can ask them!!
and does it really matter?

 

Taste it.....synthetic has a sweet taste and regular oil taste bitter.....joking. No real way other than asking the seller and hopefully they are truthful.

 

Thanks for the input just did not know if it would hurt to run conventional if synthetic was used prior

 

IMO I would just go ahead and run a full synthetic(not a synthetic blend). Its just a few bucks extra and it will also help keep the motor cool.

 

I don't think there is a problem running dyno oil after using synthetic, but as earlier stated for a couple bucks and the lower temps on My Sportster I went with the Mobil 1 15-50wt. Wally-world jugs for $22 . Problem is Wal-mart ain't selling those flavor jugs anymore.....WVleo

 

If your bike was new, it will be regular oil. Screaming Eagles (SE) are the only bikes shipped from the factory with synthetic oil. It is safe to mix synthetic and regular oil.