Hello fellow Fiat 500L Owners. Looking for engine specific antifreeze and discovered that the Fiat Dealership does have the right stuff after all. In 2013 Chrysler-Fiat switched over to a MS-12106 OAT (organic additive technology) formula, and the Owner's Manual states emphatically that you cannot mix this with "universal antifreeze" nor with HOAT (hybrid OAT) formulas.
I found the right formula at Amazon.com (Part No. 68104496AA), but they were temporarily out and sent me Mopar Part No. 68163848AB instead. Just came from the Fiat Dealership, and yes, Part No. 68163848AB supersedes the former Part No. 68104496AA. The color changes from pinkish-orange to purple. The Parts Manager assured me that this will be compatible for the 2015 Fiat. As you know, for 2016 Fiat changed over to the Chrysler engine and transmission. The label on the back of this gallon says: MS-12106 OAT.
And buy it from the Fiat Dealership. I was quoted $25.70 plus sales tax, $4.05 less than Amazon. Oh, and this is the 'concentrate' and not the pre-mix 50/50, so for ~$5 more per gallon you get twice the product. Then, just mix what you need with distilled water.
Blessings to all, and to all a very Merry Christmas! RichW