Next maintenance item for my 2015 CX5 GT is rear diff and transfer case fluid changes. The manual states they take a readily-available (and cheap) 80w90 GL5 gear oil but then in 2016 Mazda spec'd their SG1 Hypoid Gear Oil...but am I supposed to use this in lieu of 80w90 or is the SG1 only required in 2016 and up models?