The owner's manual just says to use fluid type ATF. I purchased ATF Dexron-III/Mercon on the recommendation from a tech that I talked to, but was concerned about this post: https://volvoforums.com/m_73607/tm.htmrecommending synthetic. Worst part, I don't know what's in there right now so I don't want to add an ATF fluid if it was replaced with synthetic. Any recommendations?

 

If it has ATF in there you should be able to smell it and tell. If it is the synthetic fluid it has a distinct nasty smell to it.