I'm not privileged to own a 2018 or 2019 Fit, so not aware of what Honda's specs are for the motor oil. If they specify 0W16, then fine, but if they're still at the 0w20 spec, I wouldn't use 0w16 until the vehicle is out of warranty.
For my car, the spec is 0w20 but since we live in the tropics where ambient never goes below 60 degs. F, I just use 5w20 as it's cheaper than the 0w20. I would suggest using name brand oils such as Castrol, Mobil 1, Valvoline, etc. However, I found out that Ashland Oil makes the Napa branded oils so buying a Napa Full synthetic oil is fine. Ashland is the manufacturer of Valvoline so I'm pretty sure the quality is comparable to Valvoline's. (It's kind of like how you can buy a Costco Interstate battery cheaper than the regular Interstate branded battery, but they're the same in performance.)
BTW, in terms of the oil life indicator, using it is fine in determining when to have your engine oil replaced. I've found that the Honda system is not based on mileage alone like the earlier Toyotas that had an oil change reminder system. Honda's system actually computes not only the distance driven, but what engine operating conditions are, like rpm, temperature (ambient), speed, engine load, etc. That's why if you kept track of how many miles you drove from each oil change until the 15% light came on, you'd find the mileage varies (assuming your driving habits in those two instances were noticeably different). Driving in low speed, city, stop & go type scenarios would yield much lower mileage at the 15% point than if you drove longer distance freeway type driving. So, if you're using a quality synthetic oil, you can trust using the oil life indicator as to when you need to replace the oil. (In my case, one of my cars has the oil life at 70% but I still need to replace it at that time because it's been a year since I replaced the oil & filter... yeah, a 2012 with only 26,000 miles on it!)
Last edited by garfy2008; 05-03-2019 at 03:49 PM.
Reason: more info