For a not so far away oil change on our Fusion, I'm going to be mixing 5 quarts of Service Pro oil (SN) with 0.3 quarts of Valvoline conventional (SN). I know that mixing oils isn't a problem at all, and since the car takes 5.3 quarts, I can buy 3 five quart jugs, and only have one extra single quart to get through 3 oil changes. But this time around, I'll be using 5 single quarts of Service Pro oil instead. Both the service pro oil and the VWB meet the required Ford specification for the warranty, but I want to have an official document (either from Ford or the API, or somewhere else) stating in no uncertain words that mixing oils is fine, for the sake of the warranty... in case it somehow ever becomes an issue. The OM only states to use oil that meets the Ford spec, but says nothing regarding the mixing of oils. Any links/articles? I know it shouldn't be a problem, but dealers can and will use everything against you to invalidate your warranty.