[IndyJAG]

Are there any concerns with topping off with a synthetic 15w50?  I do not know what the dealer used previous and now I'm measuring low.
Thanks

[LotusSevenMan]

Think I'd just do an oil change to get the same known oil throughout but that's just me. Hang the expense eh? 

[fredgold52]

I have heard all the urban legends about oils forming large clots when mixed, but I have never seen it in person and 've mixed oils plenty so there's been opportunity.

What I would suggest though is to top it up with petroleum based oil as that's most probably what the dealer put in it.  And if it's not, it won't matter.  Then at the first opportunity I'd do a complete oil change with whatever you plan on running in it.  That way, you'll know for sure what's in it.