[faterikcartman]

There are oil testing services for consumers that are very cheap so yes, it could be determined for sure rather cheaply and easily as you just send in a small sample.

Regarding what the dealers have told people -- are you serious? They don't care, or don't know, or can't be trusted. Like mine, your dealer will probably swear up and down that it is impossible to trade out your regular mirrors for tow mirrors.